refactor: make resonse error types validatable

src/protocol/errors/method-not-allowed.ts

@@ -17,6 +17,8 @@ import {SCError} from '../error';
 
 /**
  * An error that is returned, when the used HTTP method is not allowed on the requested route
+ *
+ * @validatable
  */
 export class SCMethodNotAllowedErrorResponse extends SCError {
   /**