prosody: optional luaEnv customization

This allows an override to add dependencies in the way that
`withExtraLibs` enabled in the past.

pkgs/servers/xmpp/prosody/default.nix

@@ -5,6 +5,7 @@
 , withDBI ? true
 # use withExtraLibs to add additional dependencies of community modules
 , withExtraLibs ? [ ]
+, withExtraLuaPackages ? _: [ ]
 , withOnlyInstalledCommunityModules ? [ ]
 , withCommunityModules ? [ ] }:
 
@@ -17,6 +18,7 @@ let
     ]
     ++ lib.optional withLibevent p.luaevent
     ++ lib.optional withDBI p.luadbi
+    ++ withExtraLuaPackages p
   );
 in
 stdenv.mkDerivation rec {

pkgs/top-level/all-packages.nix

@@ -21047,6 +21047,7 @@ with pkgs;
     # _compat can probably be removed on next minor version after 0.10.0
     lua = lua5_2_compat;
     withExtraLibs = [];
+    withExtraLuaPackages = _: [];
   };
 
   prosody-filer = callPackage ../servers/xmpp/prosody-filer { };