Signup broke: 'Database error saving new user'

Auth creates the user, then your trigger (on_auth_user_created, usually calling handle_new_user()) inserts into profiles. If that insert fails, the whole signup fails with this generic message. Reverting the UI didn't revert the database.

Find the real error in the dashboard: Logs > Postgres, filter on "error" around the time of a signup. Common causes after "add a phone number":

• phone was added as not null, and the trigger doesn't fill it. Make it nullable.
• The function references a column that got renamed.

Look at the function:

select pg_get_functiondef('public.handle_new_user'::regproc);

and make it match the table, for example:

create or replace function public.handle_new_user()
returns trigger language plpgsql security definer set search_path = ''
as $$
begin
  insert into public.profiles (id, email, phone)
  values (new.id, new.email, new.raw_user_meta_data ->> 'phone');
  return new;
end;
$$;