avahi-daemon service: add cacheEntriesMax option

nixos/modules/services/networking/avahi-daemon.nix

@@ -22,6 +22,7 @@ let
     ${optionalString (interfaces!=null) "allow-interfaces=${concatStringsSep "," interfaces}"}
     ${optionalString (domainName!=null) "domain-name=${domainName}"}
     allow-point-to-point=${yesNo allowPointToPoint}
+    ${optionalString (cacheEntriesMax!=null) "cache-entries-max=${toString cacheEntriesMax}"}
 
     [wide-area]
     enable-wide-area=${yesNo wideArea}
@@ -166,6 +167,15 @@ in
         '';
       };
 
+      cacheEntriesMax = mkOption {
+        default = null;
+        type = types.nullOr types.int;
+        description = ''
+          Number of resource records to be cached per interface. Use 0 to
+          disable caching. Avahi daemon defaults to 4096 if not set.
+        '';
+      };
+
     };
 
   };