Add allowed_to_create support for tag protection

[amimas]

Currently gitlabform can be used for branch protection with additional options of allowed_to_merge and allowed_to_push.

Gitlab has similar option for protected tags named allowed_to_create but looks like that can't be configured using gitlabform at the moment. Tag protection is only configurable using create_access_level.

This would be useful for protecting tags that are created by release bots only or by specific users.

[gdubicki]

Hi @amimas! I confirm that the current code supports only create_access_level, but it should be easy to extend it to support allowed_to_create too. PRs are welcome!

[amimas]

This is now available in v3.8.0: https://github.com/gitlabform/gitlabform/releases/tag/v3.8.0