feat(Device): add GetIp4Connectivity

See https://developer-old.gnome.org/NetworkManager/1.16/gdbus-org.freedesktop.NetworkManager.Device.html#gdbus-property-org-freedesktop-NetworkManager-Device.Ip4Connectivity

Author: guelfey

Device.go

@@ -150,6 +150,9 @@ type Device interface {
 	// True if the device exists, or False for placeholder devices that do not yet exist but could be automatically created by NetworkManager if one of their AvailableConnections was activated.
 	GetPropertyReal() (bool, error)
 
+	// The result of the last IPv4 connectivity check.
+	GetPropertyIp4Connectivity() (NmConnectivity, error)
+
 	MarshalJSON() ([]byte, error)
 }
 
@@ -309,6 +312,11 @@ func (d *device) GetPropertyReal() (bool, error) {
 	return d.getBoolProperty(DevicePropertyReal)
 }
 
+func (d *device) GetPropertyIp4Connectivity() (NmConnectivity, error) {
+	u, err := d.getUint32Property(DevicePropertyIp4Connectivity)
+	return NmConnectivity(u), err
+}
+
 func (d *device) marshalMap() (map[string]interface{}, error) {
 	Interface, err := d.GetPropertyInterface()
 	if err != nil {