Massively simplify API binding logic

Changes the API internals to use normal Laravel binding which automatically supports nested-models and can determine their relationships. This removes a lot of confusingly complex internal logic and replaces it with standard Laravel code.

This also removes a deprecated "getModel" method and fully replaces it with a "parameter" method that does stricter type-checking.

app/Http/Controllers/Api/Application/Servers/StartupController.php

@@ -34,11 +34,11 @@ class StartupController extends ApplicationApiController
      * @throws \Pterodactyl\Exceptions\Model\DataValidationException
      * @throws \Pterodactyl\Exceptions\Repository\RecordNotFoundException
      */
-    public function index(UpdateServerStartupRequest $request): array
+    public function index(UpdateServerStartupRequest $request, Server $server): array
     {
         $server = $this->modificationService
             ->setUserLevel(User::USER_LEVEL_ADMIN)
-            ->handle($request->getModel(Server::class), $request->validated());
+            ->handle($server, $request->validated());
 
         return $this->fractal->item($server)
             ->transformWith($this->getTransformer(ServerTransformer::class))