feat(invoice-ninja): add invoice ninja integration

packages/backend/src/apps/invoice-ninja/auth/is-still-verified.ts

@@ -0,0 +1,10 @@
+import { IGlobalVariable } from '@automatisch/types';
+import verifyCredentials from './verify-credentials';
+
+const isStillVerified = async ($: IGlobalVariable) => {
+  await verifyCredentials($);
+
+  return true;
+};
+
+export default isStillVerified;