feat(nixos): configure route body limits

configs/nixos/registry/route.nix

@@ -29,6 +29,12 @@
         );
       message = "UDP routes must set ports and not port.";
     }
+    {
+      assertion =
+        entries:
+        lib.all (entry: entry.value.protocol != "udp" || entry.value.clientMaxBodySize == null) entries;
+      message = "UDP routes must not set clientMaxBodySize.";
+    }
   ];
 
   type = lib.types.submodule {
@@ -64,6 +70,13 @@
         ];
         description = "Sets the UDP ports for a UDP route.";
       };
+
+      clientMaxBodySize = lib.mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        example = "1g";
+        description = "Maximum HTTP request body the reverse proxy accepts.";
+      };
     };
   };
 }