flora-6: enable gitea mail notifications, update

gitea mailer config section, see:

https://docs.gitea.io/en-us/config-cheat-sheet/#mailer-mailer

hosts/flora-6/gitea.nix

@@ -33,8 +33,9 @@
     settings = {
       mailer = {
         ENABLED = true;
-        MAILER_TYPE = "smtp";
-        HOST = "mx2.greenbaum.cloud:465";
+        PROTOCOL = "smtps";
+        SMTP_ADDR = "mx2.greenbaum.cloud";
+        SMTP_PORT = 465;
         FROM = ''"pub.solar git server" <gitea@pub.solar>'';
         USER = "admins@pub.solar";
       };
@@ -49,6 +50,7 @@
       # uncomment after initial deployment, first user is admin user
       # required to setup SSO (oauth openid-connect, keycloak auth provider)
       service.ALLOW_ONLY_EXTERNAL_REGISTRATION = true;
+      service.ENABLE_NOTIFY_MAIL = true;
       session.COOKIE_SECURE = lib.mkForce true;
     };
   };