Add a guard to deny access for some routes.

frontend/src/app/app.routes.ts

@@ -1,13 +1,16 @@
 import { Routes } from '@angular/router';
+import { alreadyAuthenticatedGuard } from './core/guard/already-authenticated.guard';
 
 export const routes: Routes = [
     { 
         path: 'login', 
-        loadComponent: () => import('./pages/login/login.component').then(module => module.LoginComponent)
+        loadComponent: () => import('./pages/login/login.component').then(module => module.LoginComponent),
+        canActivate: [alreadyAuthenticatedGuard]
     },
     { 
         path: 'signin', 
-        loadComponent: () => import('./pages/signin/signin.component').then(module => module.SigninComponent)
+        loadComponent: () => import('./pages/signin/signin.component').then(module => module.SigninComponent),
+        canActivate: [alreadyAuthenticatedGuard]
     },
     { 
         path: 'disconnect', 

frontend/src/app/core/guard/already-authenticated.guard.ts

@@ -0,0 +1,18 @@
+import { inject } from "@angular/core";
+import { CanActivateFn, Router } from "@angular/router";
+import { AuthenticationService } from "../service/authentication.service";
+import { MatSnackBar } from "@angular/material/snack-bar";
+
+export const alreadyAuthenticatedGuard: CanActivateFn = () => {
+    const authenticationService = inject(AuthenticationService);
+    const router = inject(Router);
+    const snackBar = inject(MatSnackBar);
+
+    if (authenticationService.isAuthenticated()) {
+        router.navigate(['/home']);
+        snackBar.open($localize`You can't access to this page because you are already authenticated.`, $localize`Close`, { duration: 5000 });
+        return false;
+    } else {
+        return true;
+    }
+}