[BUG] Fix eventual consistency of repository create API

[deiga]

Resolves #2604

Probably also resolves the following issues:
Resolves #897
Resolves #577
Resolves #2655
Resolves #2700
Resolves #2766

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Before the change?

• Repository creation can be flaky, since the API endpoint doesn't wait for repo creation
• Repository sweeper didn't actually work

After the change?

• Repository creation waits for up to 2 minutes before trying to modify any parts of the repository to ensure that it exists
• Some test repo names have been aligned to enable sweeper
• Added make target for sweep

Pull request checklist

• Schema migrations have been created if needed (example)
• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

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[github-actions]

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