test/mocks/cockpit: add permission function

Add the types relevant types for the `cockpit.permission` function so
that we can establish whether the user has the correct privileges to run
the frontend on-prem.

src/Utilities/useIsCockpitAdmin.tsx

@@ -0,0 +1,26 @@
+import { useEffect, useState } from 'react';
+
+import cockpit from 'cockpit';
+
+export const useIsCockpitAdmin = () => {
+  const [isAdmin, setIsAdmin] = useState(false);
+
+  useEffect(() => {
+    const permission = cockpit.permission({ admin: true });
+
+    const onChangeListener = () => {
+      setIsAdmin(permission.allowed);
+    };
+
+    permission.addEventListener('changed', onChangeListener);
+
+    // Check the initial state
+    onChangeListener();
+
+    return () => {
+      permission.removeEventListener('changed', onChangeListener);
+    };
+  }, []);
+
+  return isAdmin;
+};