enhance(backend): refine system account (#15530)

* wip

* wip

* wip

* Update SystemAccountService.ts

* Update 1740121393164-system-accounts.js

* Update DeleteAccountService.ts

* wip

* wip

* wip

* wip

* Update 1740121393164-system-accounts.js

* Update RepositoryModule.ts

* wip

* wip

* wip

* Update ApRendererService.ts

* wip

* wip

* Update SystemAccountService.ts

* fix tests

* fix tests

* fix tests

* fix tests

* fix tests

* fix tests

* add print logs

* ログが長すぎて出てないかもしれない

* fix migration

* refactor

* fix fed-tests

* Update RelayService.ts

* merge

* Update user.test.ts

* chore: emit log

* fix: tweak sleep duration

* fix: exit 1

* fix: wait for misskey processes to become healthy

* fix: longer sleep for user deletion

* fix: make sleep longer again

* デッドロック解消の試み

https://github.com/misskey-dev/misskey/issues/15005

* Revert "デッドロック解消の試み"

This reverts commit 266141f66f.

* wip

* Update SystemAccountService.ts

---------

Co-authored-by: おさむのひと <46447427+samunohito@users.noreply.github.com>
Co-authored-by: zyoshoka <107108195+zyoshoka@users.noreply.github.com>

packages/backend/src/core/DeleteAccountService.ts

@@ -5,7 +5,7 @@
 
 import { Inject, Injectable } from '@nestjs/common';
 import { Not, IsNull } from 'typeorm';
-import type { FollowingsRepository, MiUser, UsersRepository } from '@/models/_.js';
+import type { FollowingsRepository, MiMeta, MiUser, UsersRepository } from '@/models/_.js';
 import { QueueService } from '@/core/QueueService.js';
 import { DI } from '@/di-symbols.js';
 import { bindThis } from '@/decorators.js';
@@ -13,10 +13,14 @@ import { GlobalEventService } from '@/core/GlobalEventService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
 import { ApRendererService } from '@/core/activitypub/ApRendererService.js';
 import { ModerationLogService } from '@/core/ModerationLogService.js';
+import { SystemAccountService } from '@/core/SystemAccountService.js';
 
 @Injectable()
 export class DeleteAccountService {
 	constructor(
+		@Inject(DI.meta)
+		private meta: MiMeta,
+
 		@Inject(DI.usersRepository)
 		private usersRepository: UsersRepository,
 
@@ -28,6 +32,7 @@ export class DeleteAccountService {
 		private queueService: QueueService,
 		private globalEventService: GlobalEventService,
 		private moderationLogService: ModerationLogService,
+		private systemAccountService: SystemAccountService,
 	) {
 	}
 
@@ -36,8 +41,13 @@ export class DeleteAccountService {
 		id: string;
 		host: string | null;
 	}, moderator?: MiUser): Promise<void> {
+		if (this.meta.rootUserId === user.id) throw new Error('cannot delete a root account');
+
 		const _user = await this.usersRepository.findOneByOrFail({ id: user.id });
-		if (_user.isRoot) throw new Error('cannot delete a root account');
+
+		if (user.host === null && _user.username.includes('.')) {
+			throw new Error('cannot delete a system account');
+		}
 
 		if (moderator != null) {
 			this.moderationLogService.log(moderator, 'deleteAccount', {