PowerBI AppsOwnData - Configure Row Level Security

hey,

sorry for probably a stupid question.

im really new to powerbi embedded, i had my first project not a while ago, everything went well.

but now - the customer wants to apply RLS 

im using service principle and the users are autenticating thru the customer's website. 

for the life of me, i cant figure out the architucture for this thing.

i have a couple of questions:

1. how do i know which user is in the sessions?

2. since its service principle, how do i assing a role to the user?

3. where in the .NET apps own data solution do i need to insert a new code in order to apply RLS? 

i really cant figure it out, i tried searching and looking on the net but seems to hard to find this specific related topic. 

please help me... thanks alot