Merge pull request #2835 from Asquera/fixes/api

app/models/merge_request.rb

app/models/project.rb

config/routes.rb

doc/api/README.md

doc/api/groups.md

doc/api/issues.md

doc/api/merge_requests.md

doc/api/milestones.md

doc/api/notes.md

doc/api/projects.md

doc/api/repositories.md

doc/api/snippets.md

doc/api/users.md

lib/api.rb

lib/api/groups.rb

lib/api/helpers.rb

lib/api/issues.rb

lib/api/merge_requests.rb

lib/api/milestones.rb

lib/api/notes.rb