feat: NCS-63 User account implementation (#2)

User Profile info, no game before login/register, menu bar

---------

Co-authored-by: Lala, Shahd <Shahd.Lala@sybit.de>
Co-authored-by: shahdlala66 <shahd.lala66@gmail.com>
Reviewed-on: #2

src/app/services/auth-dialog.service.ts

@@ -0,0 +1,23 @@
+import { Injectable } from '@angular/core';
+import { BehaviorSubject } from 'rxjs';
+
+export type AuthDialogState = 'login' | 'register' | null;
+
+@Injectable({ providedIn: 'root' })
+export class AuthDialogService {
+    private readonly dialogStateSubject = new BehaviorSubject<AuthDialogState>(null);
+
+    readonly dialogState$ = this.dialogStateSubject.asObservable();
+
+    openLogin(): void {
+        this.dialogStateSubject.next('login');
+    }
+
+    openRegister(): void {
+        this.dialogStateSubject.next('register');
+    }
+
+    close(): void {
+        this.dialogStateSubject.next(null);
+    }
+}