ldap: Add option for NSS integration

nixos/modules/config/ldap.nix

···
         description = "Whether to include authentication against LDAP in login PAM";
       };
 
+      nsswitch = mkOption {
+        type = types.bool;
+        default = true;
+        description = "Whether to include lookup against LDAP in NSS";
+      };
+
       server = mkOption {
         example = "ldap://ldap.example.org/";
         description = "The URL of the LDAP server.";

nixos/modules/config/nsswitch.nix

···
 
   inherit (config.services.avahi) nssmdns;
   inherit (config.services.samba) nsswins;
-  ldap = config.users.ldap.enable;
+  ldap = (config.users.ldap.enable && config.users.ldap.nsswitch);
 
 in