Support Splunk Observability Cloud scaler

[sschimper-splunk]

Proposal

I've developed a custom scaler for Splunk Observability Cloud to allow for autoscaling based on a series of metrics that can be queried from Splunk Observability Cloud. Documentation is provided in kedacore/keda-docs#1477.

Scaler Source

Splunk Observability Cloud

Scaling Mechanics

Scaling based on a Metric Time Series queried from Splunk Observability Cloud via the SignalFX GO Client.

Authentication Source

Splunk Observability Access Token and Realm to be configured with the TriggerAuthentication resource.

Anything else?

I admittedly am very new to writing Go programs and collaborate with other developers via GitHub. In case I am doing something wrong, please do let me know, and I will fix it.