nixos/uhub: fix plugins, set CAP_NET_BIND_SERVICE

Fix generation of the plugins configuration and allow binding to
"privileged" ports.

nixos/modules/services/misc/uhub.nix

@@ -80,11 +80,12 @@ in {
           tls_enable = cfg.enableTLS;
           file_plugins = pkgs.writeText "uhub-plugins.conf"
             (lib.strings.concatStringsSep "\n" (map ({ plugin, settings }:
-              "plugin ${plugin} ${
-                toString
-                (lib.attrsets.mapAttrsToList (key: value: ''"${key}=${value}"'')
-                  settings)
-              }") cfg.plugins));
+              ''
+                plugin ${plugin} "${
+                  toString
+                  (lib.attrsets.mapAttrsToList (key: value: "${key}=${value}")
+                    settings)
+                }"'') cfg.plugins));
         };
       in {
         name = "uhub/${name}.conf";
@@ -104,6 +105,9 @@ in {
           ExecStart = "${pkg}/bin/uhub -c /etc/uhub/${name}.conf -L";
           ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
           DynamicUser = true;
+
+          AmbientCapabilities = "CAP_NET_BIND_SERVICE";
+          CapabilityBoundingSet = "CAP_NET_BIND_SERVICE";
         };
       };
     }) hubs;