Hey!
I'm not sure I'm writing to the correct people, but let's try anyway.
Some time ago you enabled the custom integration fields, but I'm having problem with that.
I'm trying to test it now, with a https://mocky.io 'api' but prismic fails to sync to it (copied and sanitized the example response from the docs), and since I'm having that problem, I won't start integrating to our own backend.