User-User many-to-many relation

This should be an easy question, speaking android.

A user has other users, is that possible as a relation? If not, is there any easy workaround.

My goal here is that the users them selves add each others as contacts.

For example:
User A - User B - User C -----> User A: has B and C

I have the same questions but for iOS.

I’ve already created a many to many relationship in the user table, and am fetching an (empty) collection of users (which I call “friends” in my case), I just need to know how to “add a friend”

Yes, this is totally possible with relations.