Forgejo is a newish open-source code forge system forked from Gitea

which has been rapidly gaining popularity. This change adds hosting

service support for it.
This implementation handles all of the main parts of integration for the

hosting service, including:

Authorization with the service, creating a new API token for the user

  with the correct permissions.
Basic support for getting file content (git blobs).
Post-commit review support, fetching branches, lists of commits, commit

  data, and diffs.
Bug tracker integration, including linking to issues and showing the

  bug infobox.
WebHook support for closing review requests when commits are pushed.

The only hosting service feature which is not implemented is the remote

repository listing.

Tested authorization and API token creation, including when 2FA was

  enabled.
Verified pre-commit and post-commit review functionality against a

  self-hosted Forgejo server.
Checked linking to bugs and the bug infobox.
Verified that setting up a WebHook according to the instructions worked

  correctly, and that pushing code to Forgejo properly closed relevant

  review requests.
Ran unit tests.