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/Requests/Api/Application/Servers/Databases/GetServerDatabaseRequest.php

@@ -16,15 +16,4 @@ class GetServerDatabaseRequest extends ApplicationApiRequest
      * @var int
      */
     protected $permission = AdminAcl::READ;
-
-    /**
-     * Determine if the requested server database exists.
-     */
-    public function resourceExists(): bool
-    {
-        $server = $this->route()->parameter('server');
-        $database = $this->route()->parameter('database');
-
-        return $database->server_id === $server->id;
-    }
 }