@User i'm currently doing this but get errors:

sql
CREATE OR REPLACE FUNCTION users_insert_trigger_fnc()
    RETURNS trigger AS
$$
BEGIN
    INSERT INTO public.users (id, username, avatar_url, email)
    VALUES (NEW.id, NEW.raw_user_meta_data ->> "username", NEW.raw_user_meta_data ->> "avatar_url", NEW.email);
    RETURN NEW;
END;
$$
LANGUAGE 'plpgsql';

CREATE TRIGGER users_insert_trigger
    AFTER INSERT
    ON auth.users
    FOR EACH ROW
EXECUTE PROCEDURE users_insert_trigger_fnc();

?error=server_error&error_description=Database+error+saving+new+user

I think i found it,

NEW.raw_user_meta_data ->> "username"

should have been

NEW.raw_user_meta_data ->> "user_name"

It's hard to debug as the gotrue logs aren't updating :/

All fixed now!