Add specs

app/controllers/projects/notes_controller.rb

app/models/commit_discussion.rb

app/models/concerns/resolvable_note.rb

app/models/diff_note.rb

app/models/discussion.rb

app/models/individual_note_discussion.rb

app/models/legacy_diff_discussion.rb

app/models/note.rb

app/models/out_of_context_discussion.rb

app/models/sent_notification.rb

app/services/concerns/issues/resolve_discussions.rb

app/services/notes/build_service.rb

app/views/notify/new_issue_email.html.haml

app/views/notify/new_mention_in_issue_email.html.haml

...views/notify/new_mention_in_merge_request_email.html.haml

app/views/notify/new_merge_request_email.html.haml

app/views/projects/notes/_notes.html.haml

lib/gitlab/email/handler/create_note_handler.rb

spec/controllers/projects/notes_controller_spec.rb

spec/factories/discussions.rb