deposit: Wrongly formatted xml should return a 400 bad request
Both for multipart deposit and only-metadata (atom) deposit.
This is a new kind of badly formatted which ended up in 500 internal error (server side).
This also contains movments in test (which i did not change), i just moved the xml data contextually to where it's used (clearer to read).
Related #1638 (closed)
Test Plan
tox
Migrated from D1422 (view on Phabricator)