public function rules(): array 	{ 		return [ 			'messageId' => ['required', 'string', 'max:50'], 			'msisdn' => ['required', 'string', 'max:20'], 			'to' => ['required', 'string', 'max:20'], 			'status' => ['required', 'string', 'max:20'], 			'err-code' => ['required', 'integer', 'min:0'], 		]; 	}