How to store extra user info and link primary keys with application database?

how do people handle storing extra user info / primary key linking in their databases? i assume casdoor's database is seperate from the main application database so idk how to make it all work. i see there is a syncer and wondering if that's the use purpose.

there are multiple options and features that can helps you.
So there is a custom metadata field in every user object you can fill and update with the API so you can store specific user information. But if you want to store specific user information in another database you can use the sync job. it depends on how and what specific you want to implement. I think there is no right way solution... casdoor just gives you many ways...