feat(api): add main_character_id to User (#35)

Adding main character ID from grouping to the response object of the seat API
Altering user controller to add grouping pagination

src/Http/Controllers/Api/v2/UserController.php

@@ -166,7 +166,7 @@ public function getUsers($user_id = null)
         if (! is_null($user_id))
             return new UserResource(User::findOrFail($user_id));
 
-        return UserResource::collection(User::paginate());
+        return UserResource::collection(User::with('group')->paginate());
     }
 
     /**

src/Http/Resources/UserResource.php

@@ -51,6 +51,7 @@ public function toArray($request)
             'last_login_source'        => $this->last_login_source,
             'group_id'                 => $this->group->id,
             'associated_character_ids' => $this->associatedCharacterIds(),
+            'main_character_id'        => $this->group->main_character_id,
             'token'                    => $this->refresh_token,
         ];
     }