add min loading time to loading service

apps/red-ui/src/app/services/loading.service.ts

@@ -1,11 +1,14 @@
 import { EventEmitter, Injectable } from '@angular/core';
 import { Observable } from 'rxjs';
 
+const MIN_LOADING_TIME = 300;
+
 @Injectable({
     providedIn: 'root'
 })
 export class LoadingService {
     private readonly _loadingEvent = new EventEmitter();
+    private _loadingStarted: number;
 
     get isLoading(): Observable<boolean> {
         return this._loadingEvent;
@@ -13,9 +16,18 @@ export class LoadingService {
 
     start(): void {
         this._loadingEvent.next(true);
+        this._loadingStarted = new Date().getTime();
     }
 
     stop(): void {
+        const timeDelta = new Date().getTime() - this._loadingStarted;
+        if (timeDelta < MIN_LOADING_TIME) {
+            setTimeout(() => {
+                this._loadingEvent.next(false);
+            }, MIN_LOADING_TIME - timeDelta);
+            return;
+        }
+
         this._loadingEvent.next(false);
     }
 }