Add custom logic and interaction to finish the signing proces

I starting to explore adobe sign and I have an specific use case... I need the user to complete a kind of user/password fields while completing an Adobe Sign agrement, that needs to hit a custom API that provides an answer and allow the user to sign if the anwser is ok, and that information should not remain in the signed document, is private. is this possible?

I signed up for a developer account usign this link but it doesn't seem to provide any kind of custom field interaction or something like that to try to add something in the flow. Maybe exists a way to develop some kind of plugin?