fix: review fixes (#17208)

* fix: OAuthのContent-Typeを正しく判定するように

* fix(frontend): fix outdated comments

* fix: storagePersistenceのtop-level awaitを解消

* fix

* fix(frontend): add comment

Co-Authored-By: anatawa12 <anatawa12@icloud.com>

* fix

* fix: rename `users/get-following-users-by-birthday`

* fix: fix types

* Update MkForm.vue

* refactor utility/storage.ts

---------

Co-authored-by: anatawa12 <anatawa12@icloud.com>
Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

packages/backend/src/server/oauth/OAuth2ProviderService.ts

@@ -142,7 +142,9 @@ async function discoverClientInformation(logger: Logger, httpRequestService: Htt
 			redirectUris.push(...httpLinkHeader.parse(linkHeader).get('rel', 'redirect_uri').map(r => r.uri));
 		}
 
-		if (res.headers.get('content-type')?.includes('application/json')) {
+		const contentType = res.headers.get('content-type');
+		const mediaType = contentType ? contentType.split(';')[0].trim() : null;
+		if (mediaType === 'application/json') {
 			// Client discovery via JSON document (11 July 2024 spec)
 			// https://indieauth.spec.indieweb.org/#client-metadata
 			// "Clients SHOULD have a JSON [RFC7159] document at their client_id URL containing