Resolve "`/tag` quick action on Commit comments"

What does this MR do?

Implements the /tag quick action on commit comments as described in #45663 (closed).

Are there points in the code the reviewer needs to double check?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #45663 (closed)

Notes

TODOs

• Implement Commits::TagService Commits::UpdateService
  • Tag the actual commit (aka git tag equivalent) using Tags::CreateService
  • Unit tests
  • Check authorization
• Add new tag command in InterpretService
  • Define condition based on type Commit
  • Check authorization
• Feature tests (equivalent to issues/user_uses_slash_command_spec.rb)
  • Add some more ❓
• Make sure that "Preview" is working
• Refactor find/building noteables
  • Move building noteables from AutocompleteService#commands in AutocompleteSourcesController#target
  • Build issues/merge_request (@project.issues.build) if provided type_id is empty or could not be found (in AutocompleteSourcesController#target)
    • This will solve inconsistent behavior when passing type=issue vs type=Issue
  • Remove Issueable type-check from AutocompleteService#commands
• Do not show Command applied if tagging fails
  • Currently, errors from commands are discarded
    • Example: /move non_existent_repo won't show an error nor Command applied
  • Should errors be shown?
    • ➡ already addressed in #21580 (moved)
• Verify that users are allowed to tag commits (push_code?)
  • CommitPolicy is empty ❎
  • Auto complete /tag only if user is authorized
  • Authorize user before executing Commits::TagService
    • ➡ Not needed because it's already done in Tag::CreateService.
• Tag commits asynchronously?
  • ➡ Yes, from the UX point of view
• A Commit is not Issueable
  • Avoid type checks (is_a?(Issuable)) in QuickActions::IntepretService
  • Introduce some kind of presenter to wrap Issue, MergeRequest and Commit
  • Adding methods like Commit#to_ability_name feels wrong
  • ➡ Type checks are fine and the presenter is not needed

Open questions