docs(gateway): add service discovery (XEP 0030) to README

distributor/xmpp.go

@@ -113,7 +113,7 @@ func (s *XMPPService) message(msgHead stanza.Message, t xmlstream.TokenReadEncod
 		return nil
 	}
 	from := msgHead.From.String()
-	if settings := strings.Split(conn.Settings, ":"); !(len(settings) > 1 && settings[0] == from) {
+	if settings := strings.Split(conn.Settings, ":"); len(settings) > 1 && settings[0] == from {
 		log.WithField("from", from).Info("message not from gateway, that is no notification")
 		return nil
 	}

gateway/README.md

@@ -11,6 +11,24 @@ So the XMPP-Address could be readed by Application-Server, Application and Distr
 
 The XMPP Component implements [XEP-0225](https://xmpp.org/extensions/xep-0225.html) it could be plugged in at every common server (like [ejabberd](https://docs.ejabberd.im/admin/configuration/listen/#ejabberd-service) or [Prosody](https://prosody.im/doc/components)) with an Secret and domain name.
 
+## XMPP Specials
+
+### Service Discovery XEP-0030
+As Part of the XMPP-Component we implement the following result of an Service Discovery:
+```xml
+<iq type='result'
+    from='up.chat.sum7.eu'
+    id='iq-disco-request'>
+  <query xmlns='http://jabber.org/protocol/disco#info'>
+    <identity
+        category='pubsub'
+        type='push'
+        name='Unified Push over XMPP'/>
+    <feature var='unifiedpush.org'/>
+  </query>
+</iq
+```
+
 ## Install
 
 How to configure this gateway take a look into the [config_example.toml](config_example.toml), we prefer it place it under `/etc/up-gateway.conf`