modules/snipe-it: disable upstream module

NixOS 22.05 will have a module for Snipe-IT, but it's incompatible to
our implementation and the snipe-it package is currently still at 5.x.
So we'll keep our module around and disable the upstream module when
our's is used.  This will give users of our module a chance to migrate
to upstream and upstream a change to update the package to 6.x.

modules/services/snipe-it.nix

@@ -52,6 +52,11 @@ let
 
 in {
 
+  # 22.05 has a module for this, but it's incompatible and snipe-it version is
+  # outdated, so keep this around until users had a chance to migrate to the
+  # upstream version.
+  disabledModules = [ "services/web-apps/snipe-it.nix" ];
+
   options.services.snipe-it = {
     enable = mkEnableOption "Snipe-IT free open source IT asset management";