nixos/bind: refactor zones from a list to attrset

This commit uses coercedTo to make zones a attrset instead of list.
Makes it easier to access/change zones in multiple places.

nixos/modules/services/networking/bind.nix

@@ -8,9 +8,13 @@ let
 
   bindUser = "named";
 
-  bindZoneOptions = {
+  bindZoneCoerce = list: builtins.listToAttrs (lib.forEach list (zone: { name = zone.name; value = zone; }));
+
+  bindZoneOptions = { name, config, ... }: {
+    options = {
       name = mkOption {
         type = types.str;
+        default = name;
         description = "Name of the zone.";
       };
       master = mkOption {
@@ -36,6 +40,7 @@ let
         default = "";
       };
     };
+  };
 
   confFile = pkgs.writeText "named.conf"
     ''
@@ -84,7 +89,7 @@ let
                 ${extraConfig}
               };
             '')
-          cfg.zones }
+          (attrValues cfg.zones) }
     '';
 
 in
@@ -153,18 +158,19 @@ in
 
       zones = mkOption {
         default = [];
-        type = types.listOf (types.submodule [ { options = bindZoneOptions; } ]);
+        type = with types; coercedTo (listOf attrs) bindZoneCoerce (attrsOf (types.submodule bindZoneOptions));
         description = "
           List of zones we claim authority over.
         ";
-        example = [{
-          name = "example.com";
+        example = {
+          "example.com" = {
             master = false;
             file = "/var/dns/example.com";
             masters = ["192.168.0.1"];
             slaves = [];
             extraConfig = "";
-        }];
+          };
+        };
       };
 
       extraConfig = mkOption {