Setup email provider

[chatch]

Here is how it is setup in managed supabase:
https://supabase.com/dashboard/project/pqlwxerasppsyleweruk/auth/providers?provider=Email

In self hosted we need to define an SMTP server. There is a little guidance in the docs here:
https://supabase.com/docs/guides/self-hosting/docker#configuring-an-email-server

A lot more environment variables can be seen here:
https://github.com/supabase/auth/blob/86b7de45c9432ea6ee9bd7c7e9cfe96e038fe2bc/example.env#L19

Add those variables to:

• fly toml https://github.com/cepro/supabase-host/blob/main/fly/auth/fly-auth-mgf.toml#L13
• and add fly secrets