SWORD deposit: backend server

Scholarly archives including HAL use SWORD as protocol.

Implement SWORD endpoints to permit:

• new artifacts deposit (hal id + metadata) -> injection in swh (resulting in synthetic revision)
• existing artifacts update (hal id + metadata) -> injection in swh (resulting in a new synthetic revision with parent)
• returning a status on action (swh id, hal id, eventual manifest of what was deposited)

Note:

• artifacts are limited to tarballs (.zip)
• metadata are to be defined (#717 (closed))
• Related #647 (closed)

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Migrated from T718 (view on Phabricator)