Add disconnection and minor improvements on login page.

frontend/src/app/components/header/header.component.html

@@ -2,8 +2,10 @@
     <button type="button">
         <mat-icon>menu</mat-icon>
     </button>
-    <img src="assets/images/codiki.png" alt="logo"/>
-    <span class="title">Codiki</span>
+    <a [routerLink]="['/home']">
+        <img src="assets/images/codiki.png" alt="logo"/>
+        <span class="title">Codiki</span>
+    </a>
 </div>
 <div>
     <input name="search-query" placeholder="Search something..." />
@@ -12,5 +14,10 @@
     </button>
 </div>
 <div>
-    <a [routerLink]="['/login']">Login</a>
+    <ng-container *ngIf="isAuthenticated; else anonymousRightMenu">
+        <a [routerLink]="['/disconnect']">Disconnect</a>
+    </ng-container>
+    <ng-template #anonymousRightMenu>
+        <a [routerLink]="['/login']">Login</a>
+    </ng-template>
 </div>