fix(backend): check visibility of following/followers of remote users / feat: moderators can see following/followers of all users (#14375)

* fix(backend): check visibility of following/followers of remote users

Resolves https://github.com/misskey-dev/misskey/issues/13362.

* test(backend): add tests for visibility of following/followers of remote users

* docs(changelog): update CHANGELOG.md

* feat: moderators can see following/followers of all users

* docs(changelog): update CHANGELOG.md

* refactor(backend): minor refactoring

`createPerson`と`if`の条件を統一するとともに、異常系の
処理をearly returnに追い出すための変更。

* feat(backend): moderators can see following/followers count of all users

As per https://github.com/misskey-dev/misskey/pull/14375#issuecomment-2275044908.

packages/backend/test/unit/activitypub.ts

@@ -20,7 +20,8 @@ import { CoreModule } from '@/core/CoreModule.js';
 import { FederatedInstanceService } from '@/core/FederatedInstanceService.js';
 import { LoggerService } from '@/core/LoggerService.js';
 import type { IActor, IApDocument, ICollection, IObject, IPost } from '@/core/activitypub/type.js';
-import { MiMeta, MiNote } from '@/models/_.js';
+import { MiMeta, MiNote, UserProfilesRepository } from '@/models/_.js';
+import { DI } from '@/di-symbols.js';
 import { secureRndstr } from '@/misc/secure-rndstr.js';
 import { DownloadService } from '@/core/DownloadService.js';
 import { MetaService } from '@/core/MetaService.js';
@@ -86,6 +87,7 @@ async function createRandomRemoteUser(
 }
 
 describe('ActivityPub', () => {
+	let userProfilesRepository: UserProfilesRepository;
 	let imageService: ApImageService;
 	let noteService: ApNoteService;
 	let personService: ApPersonService;
@@ -127,6 +129,8 @@ describe('ActivityPub', () => {
 		await app.init();
 		app.enableShutdownHooks();
 
+		userProfilesRepository = app.get(DI.userProfilesRepository);
+
 		noteService = app.get<ApNoteService>(ApNoteService);
 		personService = app.get<ApPersonService>(ApPersonService);
 		rendererService = app.get<ApRendererService>(ApRendererService);
@@ -205,6 +209,53 @@ describe('ActivityPub', () => {
 		});
 	});
 
+	describe('Collection visibility', () => {
+		test('Public following/followers', async () => {
+			const actor = createRandomActor();
+			actor.following = {
+				id: `${actor.id}/following`,
+				type: 'OrderedCollection',
+				totalItems: 0,
+				first: `${actor.id}/following?page=1`,
+			};
+			actor.followers = `${actor.id}/followers`;
+
+			resolver.register(actor.id, actor);
+			resolver.register(actor.followers, {
+				id: actor.followers,
+				type: 'OrderedCollection',
+				totalItems: 0,
+				first: `${actor.followers}?page=1`,
+			});
+
+			const user = await personService.createPerson(actor.id, resolver);
+			const userProfile = await userProfilesRepository.findOneByOrFail({ userId: user.id });
+
+			assert.deepStrictEqual(userProfile.followingVisibility, 'public');
+			assert.deepStrictEqual(userProfile.followersVisibility, 'public');
+		});
+
+		test('Private following/followers', async () => {
+			const actor = createRandomActor();
+			actor.following = {
+				id: `${actor.id}/following`,
+				type: 'OrderedCollection',
+				totalItems: 0,
+				// first: …
+			};
+			actor.followers = `${actor.id}/followers`;
+
+			resolver.register(actor.id, actor);
+			//resolver.register(actor.followers, { … });
+
+			const user = await personService.createPerson(actor.id, resolver);
+			const userProfile = await userProfilesRepository.findOneByOrFail({ userId: user.id });
+
+			assert.deepStrictEqual(userProfile.followingVisibility, 'private');
+			assert.deepStrictEqual(userProfile.followersVisibility, 'private');
+		});
+	});
+
 	describe('Renderer', () => {
 		test('Render an announce with visibility: followers', () => {
 			rendererService.renderAnnounce('https://example.com/notes/00example', {