Comment on graphite and VPN logins

coin/vpn/models.py

@@ -111,7 +111,9 @@ class VPNSubscription(CoinLdapSyncMixin, models.Model):
                 raise ValidationError("Endpoint {} is not in an attributed range".format(self.ipv6_endpoint))
 
     def clean(self):
-        # Generate VPN login, of the form "user_vpnX"
+        # Generate VPN login, of the form "login-vpnX".  The resulting
+        # login should not contain any ".", because graphite uses "." as a
+        # separator.
         if not self.login:
             username = self.administrative_subscription.member.ldap_cn
             vpns = VPNSubscription.objects.filter(administrative_subscription__member__ldap_cn=username)