Migrate users from 1 realm app to another


i have existing users in a realm app,
i could copy and redeploy all functions , triggers and schemas and rules from 1 realm to another realm.
but how do i migrate existing users to the other realm app and retaining user.id ?
this user id is not the collection _id, im referring to context.user.id

thank you

i could do this with firebase, but i do not know how on realm