Create API endpoint to access raw_extrinsic_metadata

They are currently only available by accessing directly swh-storage

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Migrated from T2938 (view on Phabricator)

mentioned in merge request !501 (closed)

mentioned in merge request swh-storage!694 (closed)

assigned to @vlorentz

marked this issue as related to #2088

added Metadata workflow Web app priority:Normal labels

marked this issue as related to swh/meta#3097

unassigned @vlorentz

assigned to @vlorentz

Removing the "easy hack" tag, because that's actually much harder than expected :D

marked this issue as related to swh/infra/sysadm-environment#3411 (closed)

closed