How to store user personal data in Confluence Cloud?

Hi,

I need to store user personal data in Confluence Cloud and investigating feasible solutions. One of them is storing data in cookie/local storage or using AP.cookie, but both ways are not feasible for us. See Cloud apps can't access cookies in latest Safari versions for the explanation (in short - Safari/Firefox is now blocking cookies and AP.cookie have a significant limitations for the value size).

Jira REST API provides methods to operate with user properties and it is very useful, but I can’t find the same for Confluence Cloud. Is it available via beta API?

What other options are?