previously set tenant is leaked, when RLS is disabled

[jordanstephens]

I frequently check RLS.current_tenant_id in my code to check if a current tenant has been specified, and I also use RLS.disable_for_block in a few places where no tenant is relevant. I was recently debugging a piece of code that could be run with or without a tenant. In this particular run, I was expecting no tenant to be set, but I noticed that RLS.current_tenant_id was set, even though I was within a RLS.disable_for_block block and RLS.disabled? was false. I could check for both RLS.enabled? && RLS.current_tenant_id, but I think it would be less error-prone to return nil for RLS.current_tenant_id and RLS.current_user_id if RLS.disabled? is true.

What do you think? Happy to push this further, if you think this could be improved more.

Thanks!