added modelname metric and limited lowercase labels to hostname and macaddress

main.go

@@ -190,8 +190,12 @@ func (fc *FritzboxCollector) ReportMetric(ch chan<- prometheus.Metric, m *Metric
 				lval = ""
 			}			
 			
-			// convert tolower to avoid problems with labels like hostname
+			// convert hostname and MAC tolower to avoid problems with labels
+			if(l == "HostName" || l == "MACAddress" ) {
 				labels[i] = strings.ToLower(fmt.Sprintf("%v", lval))
+			} else {
+				labels[i] = fmt.Sprintf("%v", lval)
+			}
 		}
 	}
 	

metrics.json

@@ -249,6 +249,24 @@
 		},
 		"promType": "GaugeValue"
 	},
+	{
+		"service": "urn:dslforum-org:service:DeviceInfo:1",
+		"action": "GetInfo",
+		"result": "ModelName",
+		"promDesc": {
+			"fqName": "gateway_device_modelname",
+			"help": "gateway device model name",
+			"varLabels": [
+				"gateway",
+				"Description",
+				"ModelName",
+				"ProductClass",
+				"SoftwareVersion",
+				"HardwareVersion"
+			]
+		},
+		"promType": "GaugeValue"
+	},
 	{
 		"service": "urn:dslforum-org:service:LANEthernetInterfaceConfig:1",
 		"action": "GetStatistics",