voipms: IP restriction on the setup checklist, getCDR checked against voip.ms's examples

docs/admin-guide/network.md

@@ -345,6 +345,9 @@ Someone with a stolen SIP password calling expensive international numbers is th
 real money. Keep:
 
 - international calling **off** at voip.ms and in **Outbound rules** unless you need it;
+- **IP restriction** on the voip.ms sub-account, allowing only your server's public IP: a stolen
+  trunk password used from another server skips every limit below
+  ([voip.ms setup](voipms.md#1-in-the-voipms-portal));
 - the voip.ms **balance alerts and spending limits** on;
 - the **desk phone network limit** above on if your phones are all in the office;
 - the **outside calls at once** limits (Settings → Security) as low as your office needs: per