Massive refactor

- Use contextual namespaces within Flarum\Core
- Clean up and docblock everything
- Refactor Activity/Notification blueprint stuff
- Refactor Formatter stuff
- Refactor Search stuff
- Upgrade to JSON-API 1.0
- Removed “addedPosts” and “removedPosts” relationships from discussion
API. This was used for adding/removing event posts after renaming a
discussion etc. Instead we should make an additional request to get all
new posts

Todo:
- Fix Extenders and extensions
- Get rid of repository interfaces
- Fix other bugs I’ve inevitably introduced

src/Core/Discussions/Commands/StartDiscussionHandler.php

@@ -0,0 +1,75 @@
+<?php namespace Flarum\Core\Discussions\Commands;
+
+use Flarum\Core\Discussions\Events\DiscussionWillBeSaved;
+use Flarum\Core\Forum;
+use Illuminate\Contracts\Bus\Dispatcher;
+use Flarum\Core\Discussions\Discussion;
+use Flarum\Core\Posts\Commands\PostReply;
+use Flarum\Core\Support\DispatchesEvents;
+
+class StartDiscussionHandler
+{
+    use DispatchesEvents;
+
+    /**
+     * @var Dispatcher
+     */
+    protected $bus;
+
+    /**
+     * @var Forum
+     */
+    protected $forum;
+
+    /**
+     * @param Dispatcher $bus
+     */
+    public function __construct(Dispatcher $bus, Forum $forum)
+    {
+        $this->bus = $bus;
+        $this->forum = $forum;
+    }
+
+    /**
+     * @param StartDiscussion $command
+     * @return mixed
+     */
+    public function handle(StartDiscussion $command)
+    {
+        $actor = $command->actor;
+        $data = $command->data;
+
+        $this->forum->assertCan($actor, 'startDiscussion');
+
+        // Create a new Discussion entity, persist it, and dispatch domain
+        // events. Before persistance, though, fire an event to give plugins
+        // an opportunity to alter the discussion entity based on data in the
+        // command they may have passed through in the controller.
+        $discussion = Discussion::start(
+            array_get($data, 'attributes.title'),
+            $actor
+        );
+
+        event(new DiscussionWillBeSaved($discussion, $actor, $data));
+
+        $discussion->save();
+
+        // Now that the discussion has been created, we can add the first post.
+        // We will do this by running the PostReply command.
+        $post = $this->bus->dispatch(
+            new PostReply($discussion->id, $actor, $data)
+        );
+
+        // Before we dispatch events, refresh our discussion instance's
+        // attributes as posting the reply will have changed some of them (e.g.
+        // last_time.)
+        $discussion->setRawAttributes($post->discussion->getAttributes(), true);
+        $discussion->setStartPost($post);
+
+        $this->dispatchEventsFor($discussion);
+
+        $discussion->save();
+
+        return $discussion;
+    }
+}