Classes implementing Authentication don't have anonymous attribute for additional data

Summary

I ran into this problem when trying to setup Spring Boot microservices with Redis session. I want to add additional data to org.springframework.security.core.Authentication implementation or its getDetails() or getPrincipal(), like JSON containing userID, email and etc. but I cannot do that without implementing something of my own or storing data in HttpSession attributes. I'd like to avoid both of those ways, because then I need to add the implementation classes to other microservices or access the data from HttpSessionattributes and that somehow feels kind of dirty to me. Are there plans of adding addition attribute to any of the existing implementations, like String or Object get/setAdditionalData(), or I did not find them, or I should just store it in HttpSession attributes because it's a common way of doing what I want?

Version

spring-security-core 4.1.4

The issue names org.springframework.security.core.Authentication and its getDetails() and getPrincipal() methods, but no files or tests. Start by reviewing those APIs and existing authentication implementations, then determine whether additional data belongs in the authentication contract or session attributes. Done requires a maintainer-approved scope and design.