This PR is part of a series (#11311).
Adds support for reading and creating repo-secific access tokens through the API via the `GET /users/{username}/tokens`, `POST /users/{username}/tokens`, and `DELETE /users/{username}/tokens/{id}` APIs.
Validation rules are included to [restrict repo-specific access tokens to specific scopes](https://codeberg.org/forgejo/design/issues/50#issuecomment-11093951).
## Checklist
The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).
### Tests for Go changes
(can be removed for JavaScript changes)
- I added test coverage for Go changes...
- [x] in their respective `*_test.go` for unit tests.
- [x] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I ran...
- [x] `make pr-go` before pushing
### Documentation
- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.
### Release notes
- [x] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
- [ ] This change is not visible to a Forgejo user or admin (refactor, dependency upgrade, etc.). I think there is no need to add a release note for this change.
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## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Features
- [PR](https://codeberg.org/forgejo/forgejo/pulls/11504): <!--number 11504 --><!--line 0 --><!--description cmVhZCwgY3JlYXRlLCAmIGRlbGV0ZSByZXBvLXNwZWNpZmljIGFjY2VzcyB0b2tlbnMgdmlhIEFQSQ==-->read, create, & delete repo-specific access tokens via API<!--description-->
<!--end release-notes-assistant-->
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11504
Reviewed-by: Andreas Ahlenstorf <aahlenst@noreply.codeberg.org>
Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Co-committed-by: Mathieu Fenniak <mathieu@fenniak.net>
