Annotate models

app/models/issue.rb

app/models/label.rb

app/models/label_link.rb

app/models/merge_request.rb

app/models/merge_request_diff.rb

app/models/project.rb

app/models/project_services/ci_service.rb

app/models/users_star_project.rb

spec/factories/label_links.rb

spec/factories/labels.rb

spec/factories/merge_requests.rb

spec/factories/notes.rb

spec/factories/projects.rb

spec/models/label_link_spec.rb

spec/models/label_spec.rb

spec/models/merge_request_spec.rb

spec/models/project_spec.rb