fix(handler): Support both utf-8 and utf8 charsets

Closes #120
https://encoding.spec.whatwg.org/#names-and-labels

src/handler.ts

@@ -575,11 +575,11 @@ export function createHandler<
       // TODO: handle the weight parameter "q"
       const [mediaType, ...params] = accept.split(';');
       const charset =
-        params?.find((param) => param.includes('charset=')) || 'charset=utf8'; // utf-8 is assumed when not specified;
+        params?.find((param) => param.includes('charset=')) || 'charset=utf-8'; // utf-8 is assumed when not specified;
 
       if (
         mediaType === 'application/graphql-response+json' &&
-        charset === 'charset=utf8'
+        charset === 'charset=utf-8'
       ) {
         acceptedMediaType = 'application/graphql-response+json';
         break;
@@ -590,7 +590,7 @@ export function createHandler<
         (mediaType === 'application/json' ||
           mediaType === 'application/*' ||
           mediaType === '*/*') &&
-        charset === 'charset=utf8'
+        (charset === 'charset=utf-8' || charset === 'charset=utf8')
       ) {
         acceptedMediaType = 'application/json';
         break;

tests/handler.test.ts

@@ -415,3 +415,45 @@ it('should use the default if nothing is returned from the custom request params
     ]
   `);
 });
+
+it('should accept both utf-8 and utf8 charsets ', async () => {
+  const { request } = createTHandler();
+
+  await expect(
+    request(
+      'GET',
+      { query: '{ __typename }' },
+      { accept: 'application/json; charset=utf8' },
+    ),
+  ).resolves.toMatchInlineSnapshot(`
+    [
+      "{"data":{"__typename":"Query"}}",
+      {
+        "headers": {
+          "content-type": "application/json; charset=utf-8",
+        },
+        "status": 200,
+        "statusText": "OK",
+      },
+    ]
+  `);
+
+  await expect(
+    request(
+      'GET',
+      { query: '{ __typename }' },
+      { accept: 'application/json; charset=utf-8' },
+    ),
+  ).resolves.toMatchInlineSnapshot(`
+    [
+      "{"data":{"__typename":"Query"}}",
+      {
+        "headers": {
+          "content-type": "application/json; charset=utf-8",
+        },
+        "status": 200,
+        "statusText": "OK",
+      },
+    ]
+  `);
+});