customizable muc host

+ add optional argument to the EjabberdMetrics class to customize the default muc host sub-domain

ejabberdrpc.py

@@ -13,8 +13,9 @@ class EjabberdMetrics:
     """
     class to fetch metrics per xmlrpc
     """
-    def __init__(self, url, login=None, api="rpc"):
+    def __init__(self, url, login=None, api="rpc", muc_host: str = 'conference'):
         self._login = login
+        self.muc_host = muc_host
         if api == "rpc":
             self.url = url
             self._cmd = self._rpc
@@ -156,7 +157,7 @@ class EjabberdMetrics:
         host = "global"
         if vhost is not None:
             if self._verstring.major >= 19:
-                host = "conference." + vhost
+                host = '.'.join([self.muc_host, vhost])
             else:
                 host = vhost
         result = self._cmd("muc_online_rooms", {"host": host})