Collecting extra user data

All, I’m working with a client who needs to collect some extra user data for their Ghost users. We’re still working on defining requirements, but that got me thinking.

If the client just needs to record some extra data on sign-up, that’s easy. Lots of ways to use javascript to post to a form somewhere, some of them free on the scale under consideration.

But what if the client needs their users to be able to update their information later? I’m toying around with the idea of using Supabase to store that data, and setting each user up (invisibly to the user) as a supabase user, with the Ghost cookie .sig value as their password (and the email from the cookie as their email). That sound goofy to me as I type it, but I’m thinking it’s a viable option - that .sig value is constant until the user’s email changes, and I could change the supabase login if the email changes… I think. Basically, I’d have javascript on the Ghost site getting the cookie values and making a call to Supabase. I’d have to replace some of the Portal functionality with some membership pages (and it’ll absolutely require that user’s browser runs javascript, but what doesn’t, these days?), but I think it’s doable.

What alternatives am I missing, especially ones that are cheap/free for a modest number of sign-ups and allow users to edit their information?