nixos/samba: remove services.samba.defaultShare option

It's not that difficult to define shares using standard samba config
file syntax, so why do we need the semi-configurable .defaultShare
option?

Also:
 * It uses /home/smbd and I think /home should be reserved
   for real human users.
 * If enabled, it breaks the assumption that .extraConfig continues in
   the [global] section.

Without .defaultShare there is no need for the "smbguest" user and group
either, mark them as unused.

nixos/modules/misc/ids.nix

@@ -82,7 +82,7 @@
       statsd = 69;
       transmission = 70;
       postgres = 71;
-      smbguest = 74;
+      smbguest = 74;  # unused
       varnish = 75;
       datadog = 76;
       lighttpd = 77;
@@ -220,7 +220,7 @@
       postgres = 71;
       vboxusers = 72;
       vboxsf = 73;
-      smbguest = 74;
+      smbguest = 74;  # unused
       varnish = 75;
       datadog = 76;
       lighttpd = 77;

nixos/modules/services/network-filesystems/samba.nix

@@ -6,9 +6,6 @@ let
 
   cfg = config.services.samba;
 
-  user = "smbguest";
-  group = "smbguest";
-
   logDir = "/var/log/samba";
   privateDir = "/var/samba/private";
 
@@ -16,12 +13,6 @@ let
 
   setupScript =
     ''
-      if ! test -d /home/smbd ; then
-        mkdir -p /home/smbd
-        chown ${user} /home/smbd
-        chmod a+rwx /home/smbd
-      fi
-
       if ! test -d /var/samba ; then
         mkdir -p /var/samba/locks /var/samba/cores/nmbd  /var/samba/cores/smbd /var/samba/cores/winbindd
       fi
@@ -43,13 +34,6 @@ let
       private dir = ${privateDir}
       ${optionalString cfg.syncPasswordsByPam "pam password change = true"}
 
-      ${if cfg.defaultShare.enable then ''
-      [default]
-      path = /home/smbd
-      read only = ${if cfg.defaultShare.writeable then "no" else "yes"}
-      guest ok = ${if cfg.defaultShare.guest then "yes" else "no"}
-      ''else ""}
-
       ${cfg.extraConfig}
     '';
 
@@ -149,21 +133,6 @@ in
         ";
       };
 
-      defaultShare = {
-        enable = mkOption {
-          description = "Whether to share /home/smbd as 'default'.";
-          default = false;
-        };
-        writeable = mkOption {
-          description = "Whether to allow write access to default share.";
-          default = false;
-        };
-        guest = mkOption {
-          description = "Whether to allow guest access to default share.";
-          default = true;
-        };
-      };
-
       securityType = mkOption {
         description = "Samba security type";
         default = "user";
@@ -199,14 +168,6 @@ in
 
       (mkIf config.services.samba.enable {
 
-        users.extraUsers.smbguest = {
-          description = "Samba service user";
-          group = group;
-          uid = config.ids.uids.smbguest;
-        };
-
-        users.extraGroups.smbguest.gid = config.ids.uids.smbguest;
-
         system.nssModules = optional cfg.nsswins samba;
 
         systemd = {
@@ -224,7 +185,7 @@ in
             "samba-setup" = {
               description = "Samba Setup Task";
               script = setupScript;
-              unitConfig.RequiresMountsFor = "/home/smbd /var/samba /var/log/samba";
+              unitConfig.RequiresMountsFor = "/var/samba /var/log/samba";
             };
           };
         };