When one of restarted workflows is deleted, workspace is removed, and newer restarted workflows lose their files

[VMois]

How to reproduce?

1. Restart a few workflows, so you have a sequence like this test.1, test.1.1, test.1.2.
2. Go to UI, delete test.1.1.
3. Check files for test.1.2; the workspace is empty.
4. Restart workflow test.1; it will fail.

Related code:

reana-workflow-controller/reana_workflow_controller/rest/utils.py

Line 214 in b19d0d9

def delete_workflow(workflow, all_runs=False, workspace=False):

We need to decide how to handle if a user deletes some of the restarted workflows in the middle. (1) We can only allow deleting the latest restarted workflow, which will delete all previous workflows. Or, only allow deleting the original workflow, which will delete all restarted ones.

What do you think?