Project Import from object storage via API

Summary

Currently, the Infrastructure SRE team is frequently asked by Customer Support to run manual exports or imports because they fail due to an enforced size-limit on GitLab.com on http transfers via web and API. The SRE team can intercede by running the import/export on the Rails console and then providing customer support with the archives requested. But, it's an extremely inefficient process that would be better performed self-service by our customers or Customer Support GitLab.com Administrators.

Proposed solution

Per this note, we will enable project owners to add credentials and a storage path to import an archive of their project. Following the 👣 iteration value, we will do this via API, the same way we already have in the project export.

Future considerations

This issue only adds the import storage credentials to the API. As a future iteration, we may expose this feature in the UI.

Definition of Done

• Project owners can add credentials and a storage path to export an archive of their project. This is already available via API.
• Same as above, but to import an archive of their project. (this issue)