Permanent delete from DCM4CHEE PACS

[x] Check DICOM images are actually deleted
[x] Test delete study
[x] Test delete series
[x] Clean duplicate code
[x] Update logs
[x] Delete study/series belonging to another user
[x] Check KHEOPS db
[x] Check deletion from album
[x] Check shared album
[x] Check deletion of study with event, event_series, webhooks_attempts, webhook_triggers, webhook_trigger_series
[x] Check deletion of series with event, event_series, webhooks_attempts, webhook_trigger_series
[x] Partial series deletion
[x] Check 2nd album, delete 1st
[x] Update & delete from test
[x] Check album is not deleted
[x] Check other studies/series are not impacted
[x] Check wrong password
[x] Clean github code
[x] Code review with Joël

Code Review Feedback

[x] Add Admin-Action : permanent
[x] Make KHEOPS_PROXY_PACS_DCM4CHEE_ARC optional
[x] Given that the variable is optional, update the code to reflect this eg deleteFromPacs → deleteFromDcm4che / update these to update to dcm4chee
[x] Fix secrets/password
[x] Entities : recheck the code
[x] Best way to pass secrets - new task