[Auth] Implement identity linking

[grdsdev]

Feature request

Is your feature request related to a problem? Please describe.

Implement new identity linking feature: https://supabase.com/docs/reference/javascript/auth-getuseridentities

[johndpope]

already implemented for kotlin - https://supabase.com/docs/reference/kotlin/auth-linkidentity

[johndpope]

Thanks @grdsdev -
you gotta jump onto claude ai -
I'm cranking out AI code by prompt engineering.

https://github.com/johndpope/MusicControlNet
https://github.com/johndpope/emote-hack