Upgrade helix-front to Angular 7.2 (apache#2087)

Fix security vulnerabilities in helix-front dependencies.
Upgrade helix-front dependencies to improve contributor productivity.

helix-front/client/app/cluster/cluster.component.ts

@@ -1,5 +1,5 @@
 import { Component, OnInit, ViewChild } from '@angular/core';
-import { MediaChange, ObservableMedia } from '@angular/flex-layout';
+import { MediaChange, MediaObserver } from '@angular/flex-layout';
 
 @Component({
   selector: 'hi-cluster',
@@ -13,15 +13,18 @@ export class ClusterComponent implements OnInit {
   isNarrowView: boolean;
 
   constructor(
-    protected media: ObservableMedia
+    protected media: MediaObserver
   ) { }
 
   ngOnInit() {
     // auto adjust side nav only if not embed
     this.isNarrowView = (this.media.isActive('xs') || this.media.isActive('sm'));
 
-    this.media.subscribe((change: MediaChange) => {
-      this.isNarrowView = (change.mqAlias === 'xs' || change.mqAlias === 'sm');
+    this.media.asObservable().subscribe((change: MediaChange[]) => {
+      change.forEach((item) => {
+        this.isNarrowView = (item.mqAlias === 'xs' || item.mqAlias === 'sm');
+      })
+
     });
   }
 

helix-front/client/app/core/user.service.ts

@@ -15,7 +15,7 @@ export class UserService {
     private http: HttpClient
   ) { }
 
-  public getCurrentUser(): Observable<string | object> {
+  public getCurrentUser(): Observable<unknown> {
     return this.http
       .get(`${ Settings.userAPI }/current`, { headers: this.getHeaders() }).pipe(
       catchError(_ => _));

helix-front/client/polyfills.ts

@@ -43,7 +43,6 @@ import 'core-js/es6/array';
 
 /** Evergreen browsers require these. **/
 import 'core-js/es6/reflect';
-import 'core-js/es7/reflect';
 
 
 /** ALL Firefox browsers require the following to support `@angular/animation`. **/