Add functionality to delete JWT token

Author: chiaryan

apps/frontend/src/app/services/login-store.ts

@@ -6,4 +6,10 @@ export function setToken(token: string): void {
 
 export function getToken(): string {
     return KEY in window.localStorage ? window.localStorage[KEY] : ""
+}
+
+export function deleteToken() {
+    if (KEY in window.localStorage) {
+        window.localStorage.removeItem(KEY);
+    }
 }