fix: clear state only on null

[jcosentino11]

Issue #, if available:

Description of changes:
Follow-up to #192. After UATs and more experimentation with IoT test client, I realized {"state": {}} will not clear the full shadow; only {"state": null} will accomplish this.

Why is this change necessary:

How was this change tested:
Fixed integration tests, more testing with IoT test client.

Any additional information or context required to review the change:

Checklist:

• Updated the README if applicable
• Updated or added new unit tests
• Updated or added new integration tests
• If your code makes a remote network call, it was tested with a proxy

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[github-actions]

Unit Tests Coverage Report

File	Coverage	Lines	Branches
All files	83%	89%	78%	✅
com.aws.greengrass.shadowmanager.sync.model.MergedFullShadowSyncRequest	21%	26%	15%	❌
com.aws.greengrass.shadowmanager.sync.model.LocalUpdateSyncRequest	79%	85%	73%	✅
com.aws.greengrass.shadowmanager.sync.model.Direction	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.sync.model.LocalDeleteSyncRequest	99%	98%	100%	✅
com.aws.greengrass.shadowmanager.sync.model.FullShadowSyncRequest	84%	97%	71%	✅
com.aws.greengrass.shadowmanager.sync.model.CloudDeleteSyncRequest	80%	78%	83%	✅
com.aws.greengrass.shadowmanager.sync.model.DirectionWrapper	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.sync.model.OverwriteCloudShadowRequest	98%	95%	100%	✅
com.aws.greengrass.shadowmanager.sync.model.BaseSyncRequest	83%	93%	73%	✅
com.aws.greengrass.shadowmanager.sync.model.OverwriteLocalShadowRequest	98%	95%	100%	✅
com.aws.greengrass.shadowmanager.sync.model.CloudUpdateSyncRequest	74%	76%	71%	✅
com.aws.greengrass.shadowmanager.ShadowManagerDatabase	2%	2%	0%	❌
com.aws.greengrass.shadowmanager.ShadowManager	74%	78%	71%	✅
com.aws.greengrass.shadowmanager.ShadowManagerDAOImpl	96%	97%	96%	✅
com.aws.greengrass.shadowmanager.AuthorizationHandlerWrapper	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.PubSubIntegrator	89%	93%	86%	✅
com.aws.greengrass.shadowmanager.ShadowManager$1	43%	43%	0%	❌
software.amazon.awssdk.aws.greengrass.GeneratedAbstractDeleteThingShadowOperationHandler	67%	67%	0%	✅
software.amazon.awssdk.aws.greengrass.GeneratedAbstractListNamedShadowsForThingOperationHandler	67%	67%	0%	✅
software.amazon.awssdk.aws.greengrass.GeneratedAbstractUpdateThingShadowOperationHandler	67%	67%	0%	✅
software.amazon.awssdk.aws.greengrass.GeneratedAbstractGetThingShadowOperationHandler	67%	67%	0%	✅
com.aws.greengrass.shadowmanager.util.JsonMerger	94%	98%	89%	✅
com.aws.greengrass.shadowmanager.util.SyncNodeMerger	91%	98%	84%	✅
com.aws.greengrass.shadowmanager.util.DataOwner	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.util.ShadowWriteSynchronizeHelper	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.util.Validator	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.util.JsonUtil	95%	100%	90%	✅
com.aws.greengrass.shadowmanager.ipc.BaseRequestHandler	77%	77%	0%	✅
com.aws.greengrass.shadowmanager.ipc.GetThingShadowRequestHandler	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.ipc.IpcRateLimiter	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.ipc.PubSubClientWrapper	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.ipc.UpdateThingShadowIPCHandler	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.ipc.InboundRateLimiter	94%	89%	100%	✅
com.aws.greengrass.shadowmanager.ipc.InboundRateLimiter$1	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.ipc.DeleteThingShadowRequestHandler	99%	99%	100%	✅
com.aws.greengrass.shadowmanager.ipc.UpdateThingShadowRequestHandler	93%	95%	91%	✅
com.aws.greengrass.shadowmanager.ipc.DeleteThingShadowIPCHandler	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.ipc.GetThingShadowIPCHandler	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.ipc.ListNamedShadowsForThingIPCHandler	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.ipc.model.Operation	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.ipc.model.PubSubRequest	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.sync.strategy.PeriodicSyncStrategy	63%	77%	50%	❌
com.aws.greengrass.shadowmanager.sync.strategy.SyncStrategyFactory	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.sync.strategy.BaseSyncStrategy	93%	97%	89%	✅
com.aws.greengrass.shadowmanager.sync.strategy.RealTimeSyncStrategy	93%	86%	100%	✅
com.aws.greengrass.shadowmanager.sync.IotDataPlaneClientFactory	55%	85%	25%	❌
com.aws.greengrass.shadowmanager.sync.RequestBlockingQueue	96%	99%	93%	✅
com.aws.greengrass.shadowmanager.sync.SyncHandler	71%	88%	53%	✅
com.aws.greengrass.shadowmanager.sync.IotDataPlaneClientWrapper	91%	91%	0%	✅
com.aws.greengrass.shadowmanager.sync.RequestMerger	79%	77%	81%	✅
com.aws.greengrass.shadowmanager.sync.CloudDataClient	74%	72%	77%	✅
com.aws.greengrass.shadowmanager.model.configuration.ShadowSyncConfiguration	87%	93%	82%	✅
com.aws.greengrass.shadowmanager.model.configuration.ThingShadowSyncConfiguration	76%	78%	75%	✅
com.aws.greengrass.shadowmanager.configuration.ShadowDocSizeConfiguration	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.configuration.RateLimitsConfiguration	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.configuration.ComponentConfiguration	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.sync.strategy.model.StrategyType	86%	92%	80%	✅
com.aws.greengrass.shadowmanager.sync.strategy.model.Strategy	90%	100%	80%	✅
com.aws.greengrass.shadowmanager.model.ResponseMessageBuilder	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.model.ShadowDocument	81%	89%	73%	✅
com.aws.greengrass.shadowmanager.model.ShadowStateMetadata	93%	98%	89%	✅
com.aws.greengrass.shadowmanager.model.ErrorMessage	75%	100%	50%	✅
com.aws.greengrass.shadowmanager.model.ShadowRequest	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.model.ShadowState	79%	81%	78%	✅
com.aws.greengrass.shadowmanager.model.LogEvents	100%	100%	0%	✅

Minimum allowed coverage is 65%

Generated by 🐒 cobertura-action against 861b6ea

[github-actions]

Integration Tests Coverage Report

File	Coverage	Lines	Branches
All files	72%	75%	68%	✅
com.aws.greengrass.shadowmanager.sync.model.MergedFullShadowSyncRequest	80%	85%	75%	✅
com.aws.greengrass.shadowmanager.sync.model.LocalUpdateSyncRequest	72%	74%	69%	✅
com.aws.greengrass.shadowmanager.sync.model.Direction	83%	91%	75%	✅
com.aws.greengrass.shadowmanager.sync.model.LocalDeleteSyncRequest	54%	58%	50%	✅
com.aws.greengrass.shadowmanager.sync.model.FullShadowSyncRequest	71%	79%	62%	✅
com.aws.greengrass.shadowmanager.sync.model.CloudDeleteSyncRequest	52%	54%	50%	✅
com.aws.greengrass.shadowmanager.sync.model.DirectionWrapper	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.sync.model.OverwriteCloudShadowRequest	73%	71%	75%	✅
com.aws.greengrass.shadowmanager.sync.model.BaseSyncRequest	49%	57%	41%	✅
com.aws.greengrass.shadowmanager.sync.model.OverwriteLocalShadowRequest	29%	29%	0%	❌
com.aws.greengrass.shadowmanager.sync.model.CloudUpdateSyncRequest	62%	60%	64%	✅
com.aws.greengrass.shadowmanager.ShadowManagerDatabase	60%	60%	60%	✅
com.aws.greengrass.shadowmanager.ShadowManager	89%	91%	88%	✅
com.aws.greengrass.shadowmanager.ShadowManagerDAOImpl	81%	88%	75%	✅
com.aws.greengrass.shadowmanager.AuthorizationHandlerWrapper	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.PubSubIntegrator	25%	22%	29%	❌
com.aws.greengrass.shadowmanager.ShadowManager$1	14%	14%	0%	❌
software.amazon.awssdk.aws.greengrass.GeneratedAbstractDeleteThingShadowOperationHandler	100%	100%	0%	✅
software.amazon.awssdk.aws.greengrass.GeneratedAbstractListNamedShadowsForThingOperationHandler	100%	100%	0%	✅
software.amazon.awssdk.aws.greengrass.GeneratedAbstractUpdateThingShadowOperationHandler	100%	100%	0%	✅
software.amazon.awssdk.aws.greengrass.GeneratedAbstractGetThingShadowOperationHandler	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.util.JsonMerger	66%	73%	59%	✅
com.aws.greengrass.shadowmanager.util.SyncNodeMerger	76%	88%	64%	✅
com.aws.greengrass.shadowmanager.util.DataOwner	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.util.ShadowWriteSynchronizeHelper	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.util.Validator	67%	68%	65%	✅
com.aws.greengrass.shadowmanager.util.JsonUtil	82%	90%	74%	✅
com.aws.greengrass.shadowmanager.ipc.BaseRequestHandler	77%	77%	0%	✅
com.aws.greengrass.shadowmanager.ipc.GetThingShadowRequestHandler	87%	74%	100%	✅
com.aws.greengrass.shadowmanager.ipc.IpcRateLimiter	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.ipc.PubSubClientWrapper	82%	82%	0%	✅
com.aws.greengrass.shadowmanager.ipc.UpdateThingShadowIPCHandler	55%	55%	0%	✅
com.aws.greengrass.shadowmanager.ipc.InboundRateLimiter	94%	100%	88%	✅
com.aws.greengrass.shadowmanager.ipc.InboundRateLimiter$1	75%	100%	50%	✅
com.aws.greengrass.shadowmanager.ipc.DeleteThingShadowRequestHandler	86%	72%	100%	✅
com.aws.greengrass.shadowmanager.ipc.UpdateThingShadowRequestHandler	75%	77%	73%	✅
com.aws.greengrass.shadowmanager.ipc.DeleteThingShadowIPCHandler	53%	53%	0%	✅
com.aws.greengrass.shadowmanager.ipc.GetThingShadowIPCHandler	95%	95%	0%	✅
com.aws.greengrass.shadowmanager.ipc.ListNamedShadowsForThingIPCHandler	61%	55%	67%	✅
com.aws.greengrass.shadowmanager.ipc.model.Operation	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.ipc.model.PubSubRequest	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.sync.strategy.PeriodicSyncStrategy	71%	92%	50%	✅
com.aws.greengrass.shadowmanager.sync.strategy.SyncStrategyFactory	100%	100%	100%	✅
com.aws.greengrass.shadowmanager.sync.strategy.BaseSyncStrategy	76%	85%	67%	✅
com.aws.greengrass.shadowmanager.sync.strategy.RealTimeSyncStrategy	83%	90%	75%	✅
com.aws.greengrass.shadowmanager.sync.IotDataPlaneClientFactory	77%	93%	61%	✅
com.aws.greengrass.shadowmanager.sync.RequestBlockingQueue	61%	70%	52%	✅
com.aws.greengrass.shadowmanager.sync.SyncHandler	82%	93%	71%	✅
com.aws.greengrass.shadowmanager.sync.IotDataPlaneClientWrapper	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.sync.RequestMerger	60%	67%	52%	✅
com.aws.greengrass.shadowmanager.sync.CloudDataClient	54%	51%	57%	✅
com.aws.greengrass.shadowmanager.model.configuration.ShadowSyncConfiguration	71%	81%	61%	✅
com.aws.greengrass.shadowmanager.model.configuration.ThingShadowSyncConfiguration	76%	78%	75%	✅
com.aws.greengrass.shadowmanager.configuration.ShadowDocSizeConfiguration	61%	73%	50%	✅
com.aws.greengrass.shadowmanager.configuration.RateLimitsConfiguration	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.configuration.ComponentConfiguration	100%	100%	0%	✅
com.aws.greengrass.shadowmanager.sync.strategy.model.StrategyType	55%	69%	40%	✅
com.aws.greengrass.shadowmanager.sync.strategy.model.Strategy	90%	100%	80%	✅
com.aws.greengrass.shadowmanager.model.ResponseMessageBuilder	91%	91%	0%	✅
com.aws.greengrass.shadowmanager.model.ShadowDocument	85%	93%	77%	✅
com.aws.greengrass.shadowmanager.model.ShadowStateMetadata	83%	88%	78%	✅
com.aws.greengrass.shadowmanager.model.ErrorMessage	97%	94%	100%	✅
com.aws.greengrass.shadowmanager.model.ShadowRequest	88%	77%	100%	✅
com.aws.greengrass.shadowmanager.model.ShadowState	96%	98%	94%	✅
com.aws.greengrass.shadowmanager.model.LogEvents	100%	100%	0%	✅

Minimum allowed coverage is 45%

Generated by 🐒 cobertura-action against 861b6ea