After creating a GitHub repo for a student, assign a custom permission for the associated GitHub team

[harigopal]

Is your feature request related to a problem? Please describe.
Right now, even if the team with ID specified in course.github_team_id or github_configuration.default_team_id is assigned to a repo created in Github::SetupRepositoryService, it gives this team only Read access to the repo, which is often insufficient.

It's also inflexible in that only one team can be assigned to the repo.

Describe the solution you'd like
It should be possible to configure a desired access level, which should be assigned to the repo after it has been created - probably via a queued background job. It would also be nice if this same job could handle the addition of other teams in the list. It might make sense to handle team access to a repo in this background job.

Additional context
This would mean additional API calls, but I can't see any way to avoid it.