Sending an AMP form with a serverless function

[yassinebridi]

I have a serverless function in a endpoint:

domain/api/subscribe

and defined like this:

export default async (req, res) => {
  ...
  const response = await fetch(
    `https://${DATACENTER}.api.mailchimp.com/3.0/lists/${LIST_ID}/members`,
    {
      body: JSON.stringify(data),
      headers: {
        Authorization: `apikey ${API_KEY}`,
        'Content-Type': 'application/json'
      },
      method: 'POST'
    }
  );
  ...
};

and i would like to use this endpoint with amp,
but AMP accepts only XHR, instead of fetch.

i could provide the mailchimp endpoint directly to the action-xhr property in the amp form, but again i need to provide cors headers.