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/Posts/PostsServiceProvider.php

@@ -0,0 +1,68 @@
+<?php namespace Flarum\Core\Posts;
+
+use Flarum\Core\Discussions\Discussion;
+use Flarum\Core\Users\User;
+use Flarum\Support\ServiceProvider;
+use Flarum\Extend;
+
+class PostsServiceProvider extends ServiceProvider
+{
+    /**
+     * Bootstrap the application events.
+     *
+     * @return void
+     */
+    public function boot()
+    {
+        $this->extend([
+            new Extend\PostType('Flarum\Core\Posts\CommentPost'),
+            new Extend\PostType('Flarum\Core\Posts\DiscussionRenamedPost')
+        ]);
+
+        CommentPost::setFormatter($this->app->make('flarum.formatter'));
+
+        Post::allow('*', function ($post, $user, $action) {
+            return $post->discussion->can($user, $action.'Posts') ?: null;
+        });
+
+        // When fetching a discussion's posts: if the user doesn't have permission
+        // to moderate the discussion, then they can't see posts that have been
+        // hidden by someone other than themself.
+        Discussion::addPostVisibilityScope(function ($query, User $user, Discussion $discussion) {
+            if (! $discussion->can($user, 'editPosts')) {
+                $query->where(function ($query) use ($user) {
+                    $query->whereNull('hide_user_id')
+                          ->orWhere('hide_user_id', $user->id);
+                });
+            }
+        });
+
+        Post::allow('view', function ($post, $user) {
+            return ! $post->hide_user_id || $post->can($user, 'edit') ?: null;
+        });
+
+        // A post is allowed to be edited if the user has permission to moderate
+        // the discussion which it's in, or if they are the author and the post
+        // hasn't been deleted by someone else.
+        Post::allow('edit', function ($post, $user) {
+            if ($post->discussion->can($user, 'editPosts') ||
+                ($post->user_id == $user->id && (! $post->hide_user_id || $post->hide_user_id == $user->id))
+            ) {
+                return true;
+            }
+        });
+    }
+
+    /**
+     * Register the service provider.
+     *
+     * @return void
+     */
+    public function register()
+    {
+        $this->app->bind(
+            'Flarum\Core\Posts\PostRepositoryInterface',
+            'Flarum\Core\Posts\EloquentPostRepository'
+        );
+    }
+}