Gitlabform

* **Add wildcard support for `skip_groups` and `skip_projects`.** Implements [275](https://github.com/gitlabform/gitlabform/issues/275) and [#276](https://github.com/gitlabform/gitlabform/issues/276).

Thanks to [chris-workingmouse](https://github.com/chris-workingmouse) for his contribution!

* **Add Protected branches - users allowed to push/merge** (**GitLab Premium (paid) only**), PR [273](https://github.com/gitlabform/gitlabform/pull/273).
* For `ALL_DEFINED` also skip archived projects even if they are explicitly defined in the config, unless -a flag is added - for consistency.
* **For Contributors** Add docs for running the test themselves in a Docker container and for running GitLab in Docker using a license file, for testing paid-only features.

Thanks to [florentio](https://github.com/florentio), [barryib](https://github.com/barryib) and [Pigueiras](https://github.com/Pigueiras) for their contribution!

* **Add LDAP Group Links support** (**GitLab Premium (paid) only**). Implements [140](https://github.com/gitlabform/gitlabform/issues/140).

* **Add project and group badges support**. Implements [59](https://github.com/gitlabform/gitlabform/issues/59).

* Allow 0 (no access) in Protected Tags. Fixes [172](https://github.com/gitlabform/gitlabform/issues/172).

* Exit on configuration missing `projects_and_groups` key. This will provide a helpful error message for typos made in this key. Fixes [242](https://github.com/gitlabform/gitlabform/issues/242).
* Make error messages more friendly when there is no network connection or when configuration is invalid (f.e. YAML parsing errors).
* Make the output of some processors a bit more consistent.

* Fix detecting an "empty effective config" and improve the UI related to processing groups and projects with such. Fixes [251](https://github.com/gitlabform/gitlabform/issues/251).

* Big refactoring that should make adding new features easier and faster. The main change is introducing a new way to implement "processors" - thanks to a generalized `MultipleEntitiesProcessor` class adding a new feature like Project Badges should is now as easy as implementing a class like `BadgesProcessor` and writing an acceptance test like `TestBadges`. Note that this new design may change in the near future and we are open to discussions and PRs to make it even better! We also plan to create a similar generalized `SingleEntityProcessor` class soon.

* Change the User Agent that the app uses when making requests to GitLab to a custom `GitLabForm/<gitlabform_version> (python-requests/<requests_version>)`.

* Managing project members is not incredibly slow anymore. Fixes [240](https://github.com/gitlabform/gitlabform/issues/240)

Thanks to [andrewjw](https://github.com/andrewjw) (Ocado Technology) for his contribution!

* Fixed sharing group with a subgroup. Fixes [236](https://github.com/gitlabform/gitlabform/issues/236)
* Improved re-protecting branches after updating files in them. Fail fast if the config is invalid.
* Better Docker images:
* Updated Alpine from 3.12 to 3.14,
* Started to build images in ARM64 architecture (apart from x86-64),
* Started to add tags <major_version>, <major_version>.<minor_version>. Note that Alpine-based image is the main one which gets these tags. For Debian-based images add "-buster" suffix. Implements [173](https://github.com/gitlabform/gitlabform/issues/173)

Thanks to [andrewjw](https://github.com/andrewjw) (Ocado Technology) for his contribution!

* **Added a feature to share groups with other groups, with optional enforcing.** Implements [150](https://github.com/gitlabform/gitlabform/issues/150)

Thanks to [andrewjw](https://github.com/andrewjw) (Ocado Technology) for this contribution!