FEATURE: Drafts view in user profile

* add drafts.json endpoint, user profile tab with drafts stream

* improve drafts stream display in user profile

* truncate excerpts in drafts list, better handling for resume draft action

* improve draft stream SQL query, add rspec tests

* if composer is open, quietly close it when user opens another draft from drafts stream; load PM draft only when user is in /u/username/messages (instead of /u/username)

* cleanup

* linting fixes

* apply prettier styling to modified files

* add client tests for drafts, includes a fixture for drafts.json

* improvements to code following review

* refresh drafts route when user deletes a draft open in the composer while being in the drafts route; minor prettier scss fix

* added more spec tests, deleted an acceptance test for removing drafts that was too finicky, formatting and code style fixes, added appEvent for draft:destroyed

* prettier, eslint fixes

* use "username_lower" from users table, added error handling for rejected promises

* adds guardian spec for can_see_drafts, adds improvements following code review

* move DraftsController spec to its own file

* fix failing drafts qunit test, use getOwner instead of deprecated this.container

* limit test fixture for draft.json testing to new_topic request only

test/javascripts/fixtures/draft.js.es6

@@ -0,0 +1,7 @@
+export default {
+  "/draft.json": {
+    draft:
+      '{"reply":"dum de dum da ba.","action":"createTopic","title":"dum da ba dum dum","categoryId":null,"archetypeId":"regular","metaData":null,"composerTime":540879,"typingTime":3400}',
+    draft_sequence: 0
+  }
+};