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/DiscussionState.php

@@ -0,0 +1,81 @@
+<?php namespace Flarum\Core\Discussions;
+
+use Flarum\Core\Discussions\Events\DiscussionWasRead;
+use Flarum\Core\Model;
+use Flarum\Core\Support\EventGenerator;
+use Illuminate\Database\Eloquent\Builder;
+
+/**
+ * Models a discussion-user state record in the database.
+ *
+ * Stores information about how much of a discussion a user has read. Can also
+ * be used to store other information, if the appropriate columns are added to
+ * the database, like a user's subscription status for a discussion.
+ */
+class DiscussionState extends Model
+{
+    use EventGenerator;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected $table = 'users_discussions';
+
+    /**
+     * {@inheritdoc}
+     */
+    protected static $dateAttributes = ['read_time'];
+
+    /**
+     * Mark the discussion as being read up to a certain point. Raises the
+     * DiscussionWasRead event.
+     *
+     * @param int $number
+     * @return $this
+     */
+    public function read($number)
+    {
+        if ($number > $this->read_number) {
+            $this->read_number = $number;
+            $this->read_time   = time();
+
+            $this->raise(new DiscussionWasRead($this));
+        }
+
+        return $this;
+    }
+
+    /**
+     * Define the relationship with the discussion that this state is for.
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
+     */
+    public function discussion()
+    {
+        return $this->belongsTo('Flarum\Core\Discussions\Discussion', 'discussion_id');
+    }
+
+    /**
+     * Define the relationship with the user that this state is for.
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
+     */
+    public function user()
+    {
+        return $this->belongsTo('Flarum\Core\Users\User', 'user_id');
+    }
+
+    /**
+     * Set the keys for a save update query.
+     *
+     * @param Builder $query
+     * @return Builder
+     */
+    protected function setKeysForSaveQuery(Builder $query)
+    {
+        $query->where('discussion_id', $this->discussion_id)
+              ->where('user_id', $this->user_id);
+
+        return $query;
+    }
+}