Set headers/cookies for error responses from hooks

Describe the problem

It's possible to end up in a state in an app where a cookie value of some kind is causing an error. For instance, you might have started an authentication request, only to have the request fail for some reason. If the request details are stored in a cookie, then the user might keep reloading the page and keep seeing an error page. We have this issue with our oauth-based login system.

We want to use handleError to handle these errors so we don't need to manually handle them all over the place, and instead can just throw when something goes wrong. But we need to clear the cookie which that error occurs, so the user gets back into a non-broken state.

Describe the proposed solution

Maybe handleError could return headers that get appended to the response?

export function handleError({ error, event }) {
  const errorId = crypto.randomUUID();
  // example integration with https://sentry.io/
  Sentry.captureException(error, { event, errorId });
 
  return {
    message: 'Whoops!',
    headers: {
      'Set-Cookie': '...',
    },
    errorId
  };
}

Alternatives considered

No response

Importance

would make my life easier

Additional Information

No response

Start at the handleError hook and trace how errors become responses. Determine where headers from the hook could be incorporated, then verify that a returned Set-Cookie value reaches the error response and add coverage for the behavior.