Extend new deposit endpoint to support metadata-only deposits

Extend same deposit endpoint

Depositing metadata is SWORD compliant - see http://swordapp.github.io/SWORDv2-Profile/SWORDProfile.html#protocoloperations_creatingresource_entry)

It is required to use the same endpoint as the regular deposit.

Although, it might be challenging to do so, since the metadata deposit requires a SWHID and the process that follows is quite different from the deposit.

---

Migrated from T2537 (view on Phabricator)