[WIP] Fix ban by software version, some other under-hood changes

- Use updated version of upstream go-xmpp + fixes on client-side
- Introduce golangci-lint v2 + fixes
- Move especially noisy debugging stuff to separate config handles to be able to switch them off
- Add a bit debug to ban by software path

vendor/github.com/xmppo/go-xmpp/xmpp_ping.go

@@ -0,0 +1,57 @@
+package xmpp
+
+import (
+	"fmt"
+	"time"
+)
+
+func (c *Client) PingC2S(jid, server string) error {
+	if jid == "" {
+		jid = c.jid
+	}
+	if server == "" {
+		server = c.domain
+	}
+	_, err := fmt.Fprintf(c.stanzaWriter, "<iq from='%s' to='%s' id='%s' type='get'>"+
+		"<ping xmlns='urn:xmpp:ping'/>"+
+		"</iq>\n",
+		xmlEscape(jid), xmlEscape(server), getUUID())
+	return err
+}
+
+func (c *Client) PingS2S(fromServer, toServer string) error {
+	_, err := fmt.Fprintf(c.stanzaWriter, "<iq from='%s' to='%s' id='%s' type='get'>"+
+		"<ping xmlns='urn:xmpp:ping'/>"+
+		"</iq>\n",
+		xmlEscape(fromServer), xmlEscape(toServer), getUUID())
+	return err
+}
+
+func (c *Client) SendResultPing(id, toServer string) error {
+	_, err := fmt.Fprintf(c.stanzaWriter, "<iq type='result' to='%s' id='%s'/>\n",
+		xmlEscape(toServer), xmlEscape(id))
+	return err
+}
+
+func (c *Client) sendPeriodicPings() {
+	for range c.periodicPingTicker.C {
+		// Reset ticker for periodic pings if configured.
+		if c.periodicPings {
+			c.periodicPingTicker.Reset(c.periodicPingPeriod)
+		}
+		c.periodicPingID = getUUID()
+		c.periodicPingReply = false
+		_, err := fmt.Fprintf(c.stanzaWriter, "<iq from='%s' to='%s' id='%s' type='get'>"+
+			"<ping xmlns='urn:xmpp:ping'/></iq>\n",
+			xmlEscape(c.jid), xmlEscape(c.domain), c.periodicPingID)
+		if err != nil {
+			c.Close()
+		}
+		time.Sleep(c.periodicPingTimeout)
+		if !c.periodicPingReply {
+			c.shutdown = true
+			fmt.Fprintf(c.stanzaWriter, "</stream:stream>\n")
+			c.conn.Close()
+		}
+	}
+}