feat: preserved usernames

Resolve #10704

packages/backend/src/core/SignupService.ts

@@ -13,8 +13,9 @@ import { UsedUsername } from '@/models/entities/UsedUsername.js';
 import generateUserToken from '@/misc/generate-native-user-token.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
 import { bindThis } from '@/decorators.js';
-import UsersChart from './chart/charts/users.js';
-import { UtilityService } from './UtilityService.js';
+import UsersChart from '@/core/chart/charts/users.js';
+import { UtilityService } from '@/core/UtilityService.js';
+import { MetaService } from '@/core/MetaService.js';
 
 @Injectable()
 export class SignupService {
@@ -34,6 +35,7 @@ export class SignupService {
 		private utilityService: UtilityService,
 		private userEntityService: UserEntityService,
 		private idService: IdService,
+		private metaService: MetaService,
 		private usersChart: UsersChart,
 	) {
 	}
@@ -44,6 +46,7 @@ export class SignupService {
 		password?: string | null;
 		passwordHash?: UserProfile['password'] | null;
 		host?: string | null;
+		ignorePreservedUsernames?: boolean;
 	}) {
 		const { username, password, passwordHash, host } = opts;
 		let hash = passwordHash;
@@ -76,6 +79,14 @@ export class SignupService {
 		if (await this.usedUsernamesRepository.findOneBy({ username: username.toLowerCase() })) {
 			throw new Error('USED_USERNAME');
 		}
+
+		if (!opts.ignorePreservedUsernames) {
+			const instance = await this.metaService.fetch(true);
+			const isPreserved = instance.preservedUsernames.map(x => x.toLowerCase()).includes(username.toLowerCase());
+			if (isPreserved) {
+				throw new Error('USED_USERNAME');
+			}
+		}
 	
 		const keyPair = await new Promise<string[]>((res, rej) =>
 			generateKeyPair('rsa', {