How to save progress and allow resume if a survey is closed before completion step is reached

[malantessa]

Hi! Thanks for the great package, it has helped me a lot.

I'm working on an app where there are multiple surveys a user can choose from on the home page. I want the survey to work in such a way that closing it before the completion step has been completed saves the progress and answers the user has given and if they re-open the same survey, they can pick up where they left off.

Can you provide any advice on if and how this might be possible? I'm guessing a custom SurveyController is necessary, but I'm not quite sure where to start with that.