Update serializer

Use constants in enctype.

packages/iceform-next/src/utils/serialization.ts

@@ -1,7 +1,7 @@
 import { IncomingMessage } from 'http';
 import { getFormValues } from '@theoryofnekomata/formxtra';
 import {
-	ENCTYPE_APPLICATION_JSON,
+	ENCTYPE_APPLICATION_JSON, ENCTYPE_APPLICATION_OCTET_STREAM,
 	ENCTYPE_MULTIPART_FORM_DATA,
 	ENCTYPE_X_WWW_FORM_URLENCODED,
 } from '../common';
@@ -66,7 +66,7 @@ export const DEFAULT_ENCTYPE_DESERIALIZERS: EncTypeDeserializerMap = {
 
 export const deserializeBody = async (params: DeserializeBodyParams) => {
 	const { req, deserializers = DEFAULT_ENCTYPE_DESERIALIZERS } = params;
-	const contentType = req.headers['content-type'] ?? 'application/octet-stream';
+	const contentType = req.headers['content-type'] ?? ENCTYPE_APPLICATION_OCTET_STREAM;
 
 	if (contentType?.startsWith(`${ENCTYPE_MULTIPART_FORM_DATA};`)) {
 		return parseMultipartFormData(req);