fix(repository): Move backend code into subdirectory

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

backend/src/groups/groups.module.ts

@@ -0,0 +1,18 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+
+import { LoggerModule } from '../logger/logger.module';
+import { Group } from './group.entity';
+import { GroupsService } from './groups.service';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([Group]), LoggerModule],
+  providers: [GroupsService],
+  exports: [GroupsService],
+})
+export class GroupsModule {}