[chore] adapt message sent by the syslog data sender to fit rfc5424 f…

…ormat (open-telemetry#35201)

**Description:** This PR adapts the syslog data sender to generate valid
messages adhering to the RFC5424 format. Previously, the data sender
generated invalid messages causing the syslog message parser to fail
(due to empty attribute values, a missing version number and SDID

**Link to tracking Issue:** -

**Testing:** -

**Documentation:** -

---------

Signed-off-by: Florian Bacher <[email protected]>

testbed/datasenders/syslog.go

@@ -91,14 +91,20 @@ func (f *SyslogWriter) GenConfigYAMLStr() string {
 func (f *SyslogWriter) Send(lr plog.LogRecord) error {
 	ts := time.Unix(int64(lr.Timestamp()/1_000_000_000), int64(lr.Timestamp()%1_000_000_000)).Format(time.RFC3339Nano)
 	sdid := strings.Builder{}
-	sdid.WriteString(fmt.Sprintf("%s=\"%s\" ", "trace_id", lr.TraceID()))
-	sdid.WriteString(fmt.Sprintf("%s=\"%s\" ", "span_id", lr.SpanID()))
+	if lr.TraceID().String() != "" {
+		sdid.WriteString(fmt.Sprintf("%s=\"%s\" ", "trace_id", lr.TraceID()))
+	}
+	if lr.SpanID().String() != "" {
+		sdid.WriteString(fmt.Sprintf("%s=\"%s\" ", "span_id", lr.SpanID()))
+	}
 	sdid.WriteString(fmt.Sprintf("%s=\"%d\" ", "trace_flags", lr.Flags()))
 	lr.Attributes().Range(func(k string, v pcommon.Value) bool {
-		sdid.WriteString(fmt.Sprintf("%s=\"%s\" ", k, v.Str()))
+		if v.Str() != "" {
+			sdid.WriteString(fmt.Sprintf("%s=\"%s\" ", k, v.Str()))
+		}
 		return true
 	})
-	msg := fmt.Sprintf("<166> %s 127.0.0.1 - - - [%s] %s\n", ts, sdid.String(), lr.Body().Str())
+	msg := fmt.Sprintf("<166>1 %s 127.0.0.1 - - - [test@12345 %s] %s\n", ts, strings.TrimSpace(sdid.String()), lr.Body().Str())
 
 	f.buf = append(f.buf, msg)
 	return f.SendCheck()