message: More robust "Content-Type: application/json" test (this one works)
diff: @@ -47,8 +47,8 @@ export const AuthProvider: FC = ({ children }) => {
  if (!req.ok) {
  throw new Error(`Failed to get /whoami ${req.statusText}`);
  }
  - if (req.headers.get('content-type') !== 'application/json') {
  - throw new Error('Failed to GET /whoami JSON data: backend may be missing _handler.js.');
  + if (!req.headers.get('content-type')!.startsWith('application/json')) {
  + throw new Error('Failed to GET /whoami JSON data: backend may be missing file _handler.js.');
  }
  return req.json();
  }, []);
  