refactor: pretty much the whole backend module hierarchy

backend/src/user-data/user-data.module.ts

@@ -0,0 +1,12 @@
+import { Module } from '@nestjs/common';
+import { LibraryModule } from './library/library.module';
+import { PlayStatesModule } from './play-state/play-states.module';
+import { UserDataController } from './user-data.controller';
+import { UsersModule } from 'src/users/users.module';
+
+@Module({
+  providers: [],
+  controllers: [UserDataController],
+  imports: [PlayStatesModule, LibraryModule, UsersModule],
+})
+export class UserDataModule {}