Add group management actions to API

src/Core/Groups/GroupRepository.php

@@ -0,0 +1,50 @@
+<?php namespace Flarum\Core\Groups;
+
+use Flarum\Core\Users\User;
+use Illuminate\Database\Eloquent\Builder;
+
+class GroupRepository
+{
+    /**
+     * Get a new query builder for the groups table.
+     *
+     * @return Builder
+     */
+    public function query()
+    {
+        return User::query();
+    }
+
+    /**
+     * Find a user by ID, optionally making sure it is visible to a certain
+     * user, or throw an exception.
+     *
+     * @param int $id
+     * @param User $actor
+     * @return Group
+     *
+     * @throws \Illuminate\Database\Eloquent\ModelNotFoundException
+     */
+    public function findOrFail($id, User $actor = null)
+    {
+        $query = Group::where('id', $id);
+
+        return $this->scopeVisibleTo($query, $actor)->firstOrFail();
+    }
+
+    /**
+     * Scope a query to only include records that are visible to a user.
+     *
+     * @param Builder $query
+     * @param User $actor
+     * @return Builder
+     */
+    protected function scopeVisibleTo(Builder $query, User $actor = null)
+    {
+        if ($actor !== null) {
+            $query->whereVisibleTo($actor);
+        }
+
+        return $query;
+    }
+}