[Minor] Lua_util: Add lupa.filters.pbkdf

lualib/lua_util.lua

@@ -31,11 +31,17 @@ local space = lpeg.S' \t\n\v\f\r'
 local nospace = 1 - space
 local ptrim = space^0 * lpeg.C((space^0 * nospace^1)^0)
 local match = lpeg.match
+
 lupa.configure{
   keep_trailing_newline = true,
   autoescape = false,
 }
 
+lupa.filters.pbkdf = function(s)
+  local cr = require "rspamd_cryptobox"
+  return cr.pbkdf(s)
+end
+
 local function rspamd_str_split(s, sep)
   local gr
   if not sep then