nixos/consul: fix consul alerts enable

nixos/modules/services/networking/consul.nix

@@ -106,6 +106,12 @@ in
       alerts = {
         enable = mkEnableOption "Whether to enable consul-alerts";
 
+        package = mkOption {
+          description = "Package to use for consul-alerts.";
+          default = pkgs.consul-alerts;
+          type = types.package;
+        };
+
         listenAddr = mkOption {
           description = "Api listening address.";
           default = "localhost:9000";
@@ -135,7 +141,8 @@ in
 
   };
 
-  config = mkIf cfg.enable {
+  config = mkIf cfg.enable (
+    mkMerge [{
 
       users.extraUsers."consul" = {
         description = "Consul agent daemon user";
@@ -207,8 +214,10 @@ in
           echo "}" >> /etc/consul-addrs.json
         '';
       };
+    }
 
-    systemd.services.consul-alerts = mkIf (cfg.alerts.enable) {
+    (mkIf (cfg.alerts.enable) {
+      systemd.services.consul-alerts = {
         wantedBy = [ "multi-user.target" ];
         after = [ "consul.service" ];
 
@@ -216,15 +225,17 @@ in
 
         serviceConfig = {
           ExecStart = ''
-          ${pkgs.consul-alerts}/bin/consul-alerts start \
+            ${cfg.alerts.package}/bin/consul-alerts start \
               --alert-addr=${cfg.alerts.listenAddr} \
               --consul-addr=${cfg.alerts.consulAddr} \
               ${optionalString cfg.alerts.watchChecks "--watch-checks"} \
               ${optionalString cfg.alerts.watchEvents "--watch-events"}
           '';
           User = if cfg.dropPrivileges then "consul" else null;
+          Restart = "on-failure";
         };
       };
+    })
 
-  };
+  ]);
 }