Unhandled 400 error while creating an existing worker repository from Gitlab

Happens when creating a worker repository from a Gitlab project that has already been created (in any corpus).
Selected corpus is not part of the Repository constraint (url unicity only).

• Do not raise the 400 error
• A message explaining that a created Repository is automatically available for any corpora (if its corpus is readable by the user) would be clearer and help understanding a repository cannot be imported into multiple corpora.