Draft: Add tombstone delete

Summary

Added tombstone delete to the Service and logs now differentiate between purge and delete.

This was tested against the GWDG Cordra instance and not the testbed. Set to draft because while it passes the Pipeline, the changes depend on the SDK MR.

Check List for the Author

• All automated tests pass
• Reference related issues
• Appropriate user and developer documentation for new code
• Annotations in code (Gitlab comments)

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Appropriate user and developer documentation for new code
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.

requested review from @henrik and @timm

assigned to @i.nueske

marked the checklist item All automated tests pass as completed

marked the checklist item Reference related issues as completed

Strictly speaking, Purge is not an Operation. However, as delete and purge have very different outcomes, the log should probably indicate which was run. This was the easiest solution.

marked the checklist item Annotations in code (Gitlab comments) as completed

unassigned @i.nueske