Disallow unauthenticated senders

This stops unauthenticated users from sending unauthorized emails.

Example:

`swaks -t matteo@mail.saloniamatteo.top --header "Subject: Unauthorized Email" --body "This email should not go through." --server mail.saloniamatteo.top`

Before this patch, any user could run the command above, without any authentication, and the server would gladly accept the incoming mail.
Now, the email is rejected, and the email server only allows authenticated users.

emailwiz.sh

@@ -81,6 +81,7 @@ postconf -e "smtpd_sasl_type = dovecot"
 postconf -e "smtpd_sasl_path = private/auth"
 
 # Sender and recipient restrictions
+postconf -e "smtpd_sender_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unknown_sender_domain, reject_unauth_pipelining, reject_non_fqdn_sender, reject_sender_login_mismatch, reject_authenticated_sender_login_mismatch, reject_known_sender_login_mismatch, reject_unauthenticated_sender_login_mismatch"
 postconf -e "smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination"
 
 # NOTE: the trailing slash here, or for any directory name in the home_mailbox