Log some infos, sign using dkim separator

data/conf/rspamd/local.d/dkim.conf

@@ -1,17 +1,25 @@
 sign_condition =<<EOD
 return function(task)
   local from = task:get_from('smtp')
+  local rspamd_logger = require "rspamd_logger"
+  if not task:get_user() then
+    rspamd_logger.infox(task, "Skip DKIM signing for unauthorized user")
+    return false
+  end
   if from and from[1]['addr'] then
     lastAtSymbol = from[1]['addr']:find("[^%@]+$")
     local domain = from[1]['addr']:sub(lastAtSymbol, #from[1]['addr'])
-                local keyfile = io.open("/etc/rspamd/dkim/keys/" .. domain .. ".default")
+    local keyfile = io.open("/data/dkim/keys/" .. domain .. ".dkim")
     if keyfile then
+      rspamd_logger.infox(task, "DKIM signing mail for authorized user of domain %s", domain)
       keyfile:close()
       return {
-                                key = "/etc/rspamd/dkim/keys/" .. domain .. ".default",
+        key = "/data/dkim/keys/" .. domain .. ".dkim",
         domain = domain,
-                                selector = "default"
+        selector = "dkim"
       }
+    else
+      rspamd_logger.infox(task, "Authorized user, but no key file for domain %s - skipped DKIM signing", domain)
     end
   end
   return false