return a `Vary: Accept` header for all dual-format endpoints #365 (#13044)

`/users/:user`, `/@:user`, `/notes/:note` return different responses
depending on the request's `Accept:` header. If we don't consistently
return a `Vary: Accept` header, browsers and caching proxies will get
confused, and return AP representations when HTML was requested, or
vice versa.

Co-authored-by: dakkar <dakkar@thenautilus.net>
Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>

packages/backend/src/server/ActivityPubServerService.ts

@@ -648,6 +648,8 @@ export class ActivityPubServerService {
 		});
 
 		fastify.get<{ Params: { user: string; } }>('/users/:user', { constraints: { apOrHtml: 'ap' } }, async (request, reply) => {
+			vary(reply.raw, 'Accept');
+
 			const userId = request.params.user;
 
 			const user = await this.usersRepository.findOneBy({
@@ -660,6 +662,8 @@ export class ActivityPubServerService {
 		});
 
 		fastify.get<{ Params: { user: string; } }>('/@:user', { constraints: { apOrHtml: 'ap' } }, async (request, reply) => {
+			vary(reply.raw, 'Accept');
+
 			const user = await this.usersRepository.findOneBy({
 				usernameLower: request.params.user.toLowerCase(),
 				host: IsNull(),

packages/backend/src/server/web/ClientServerService.ts

@@ -476,6 +476,8 @@ export class ClientServerService {
 				isSuspended: false,
 			});
 
+			vary(reply.raw, 'Accept');
+
 			if (user != null) {
 				const profile = await this.userProfilesRepository.findOneByOrFail({ userId: user.id });
 				const meta = await this.metaService.fetch();
@@ -515,6 +517,8 @@ export class ClientServerService {
 				return;
 			}
 
+			vary(reply.raw, 'Accept');
+
 			reply.redirect(`/@${user.username}${ user.host == null ? '' : '@' + user.host}`);
 		});