Index flag user link

Problem/Motivation

I have a search api solr views list of users where I need to put a "follow user" flag link.
With only views (without solr) I can add "follow" flag -link.
But with search API I cant find a solution how to add / index a "user flag".
Is this even possible with users?

In the indes processor page there is :
Switching on will enable indexing flags on * content
So does it mean that only content flags can be indexed but no user flags?

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes