Add custom HTTP interceptor and spinner service for request handling; update CORS settings

jambotron-ui/src/app/helpers/custom-http-interceptor.spec.ts

@@ -0,0 +1,7 @@
+import { CustomHttpInterceptor } from './custom-http-interceptor';
+
+describe('CustomHttpInterceptor', () => {
+  it('should create an instance', () => {
+    expect(new CustomHttpInterceptor()).toBeTruthy();
+  });
+});

jambotron-ui/src/app/helpers/custom-http-interceptor.ts

@@ -0,0 +1,24 @@
+import {HttpEvent, HttpHandler, HttpInterceptor, HttpRequest, HttpResponse} from '@angular/common/http';
+import {Observable, tap} from 'rxjs';
+import {SpinnerService} from '../services/spinner.service';
+import {Injectable} from '@angular/core';
+
+@Injectable()
+export class CustomHttpInterceptor implements HttpInterceptor {
+
+  constructor(private spinnerService: SpinnerService) { }
+
+  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
+
+    this.spinnerService.show();
+
+    return next.handle(req)
+      .pipe(tap((event: HttpEvent<any>) => {
+        if (event instanceof HttpResponse) {
+          this.spinnerService.hide();
+        }
+      }, (error) => {
+        this.spinnerService.hide();
+      }));
+  }
+}