refactor: pretty much the whole backend module hierarchy

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

@@ -0,0 +1,14 @@
+import { Module } from '@nestjs/common';
+import { MetadataModule } from 'src/metadata/metadata.module';
+import { LibraryController } from './library.controller';
+import { libraryProviders } from './library.providers';
+import { LibraryService } from './library.service';
+import { UsersModule } from 'src/users/users.module';
+
+@Module({
+  providers: [...libraryProviders, LibraryService],
+  controllers: [LibraryController],
+  imports: [MetadataModule, UsersModule],
+  exports: [LibraryService],
+})
+export class LibraryModule {}