Add demo mode

backend/src/managers/demo/demomanager.service.ts

@@ -0,0 +1,18 @@
+import { Injectable, Logger } from '@nestjs/common';
+import { ImageDBService } from '../../collections/imagedb/imagedb.service';
+
+@Injectable()
+export class DemoManagerService {
+  private readonly logger = new Logger('DemoManagerService');
+
+  constructor(private readonly imagesService: ImageDBService) {}
+
+  private async executeAsync() {
+    this.logger.log('Executing demo cleanup');
+    await this.imagesService.deleteAll();
+  }
+
+  public execute() {
+    this.executeAsync().catch(this.logger.error);
+  }
+}