cli: improve deletion of workflows with attached interactive sessions

Current behaviour

When a user deletes a workflow, its workspace is deleted, however the user is not warned that any interactive notebook sessions started on the workspace will be kept running (on a now-empty workspace).

For example, run an test workflow:

$ reana-client run -w test
...
$ reana-client status -w test
NAME   RUN_NUMBER   CREATED               STARTED               ENDED                 STATUS     PROGRESS
test   1            2023-01-27T11:01:52   2023-01-27T11:02:03   2023-01-27T11:02:09   finished   1/1

Open a notebook on the test workflow's workspace:

$ reana-client open -w test

Delete the workflow:

$ reana-client delete -w test

The notebook session will remain active, even though all the files under the workspace had been removed.

(Also, reana-client list --sessions is not showing anything unless one does reana-client list --sessions --show-deleted-runs.)

Expected behaviour

It would be useful to do one of the following to make it more transparent:

Option A (gentle): detect whether there is an open session for the workflow that the user would like to delete, and warn about this and refuse to continue (so that user does not loose any work) and ask the user to close the session first (and provide a command to copy/past to run that);
Option B (harsh): automatically delete also any open sessions attached to the workspace the user want to delete (trusting that the deletion of a workflow's workspace should cascade into whatever notebooks were opened on this workspace).

We may also want to introduce a new CLI option, such as delete --include-session, that would do the above, with the default being "off" for gentle behaviour, and "on" for the harsh behaviour.

reanahub / reana-client

cli: improve deletion of workflows with attached interactive sessions #649