A client can access collections.

- DELETE EM-IRI: deletes a deposit reference (only on partial one)
- DELETE EDIT/SE IRI: delete archive endpoint (only on partial one)
- Add tests around both

Also, refactor code

Beware:

- Update means replace existing metadata/archive with new ones.
In effect, this replaces the previous deposit information.

- Add: add new metadata/archive to existing deposit

To:
- update existing metadata to an existing deposit
- add new metadata/archive to existing deposit
- display the actual deposit's metadata

And not the status endpoint