Programmatically signIn a user via service role

I have a use case where I'm essentially implementing something similar to a token exchange flow (

I'm essentially getting a valid token for a game launcher platform, then I create a user if doesn't exist on my Supabase app, and what I want to do is return my supabase token. Right now this seems needlessly complex (I *think* the only way to achieve this is via generating a custom OTP and immediately verifying it? Which seems clumsy).

What I really need is to be able to programmatically signIn() an arbitrary user using their email or phone via the service role, without having to do OTP or present any password.