urlwatch: optionalise custom sendmail

krebs/3modules/urlwatch.nix

@@ -17,6 +17,8 @@ let
   api = {
     enable = mkEnableOption "krebs.urlwatch";
 
+    customSendmail.enable = mkEnableOption "krebs.urlwatch.customSendmail";
+
     dataDir = mkOption {
       type = types.str;
       default = "/var/lib/urlwatch";
@@ -158,6 +160,7 @@ let
               --urls=${shell.escape urlsFile} \
             > changes || :
 
+          ${optionalString cfg.customSendmail.enable /* sh */ ''
             if test -s changes; then
               {
                 echo Date: $(date -R)
@@ -171,6 +174,7 @@ let
                 cat changes
               } | /run/wrappers/bin/sendmail -t
             fi
+          ''}
         '';
       };
     };