feat: update DiscoveryMessage struct and add API documentation

internal/handler/discovery.go

@@ -162,7 +162,7 @@ func (h *Handler) updateExistingDevice(msg DiscoveryMessage, previousStatusID in
 	return nil
 }
 
-// getDeviceSensors retrieves existing sensors for a device
+// getDeviceSensors retrieves existing sensors for a device<
 func getDeviceSensors(tx *sql.Tx, deviceID string) (map[string]DiscoverySensorPayload, error) {
 	rows, err := tx.Query(
 		"SELECT BIN_TO_UUID(id), name, type, data_type_id FROM sensors WHERE device_id = UUID_TO_BIN(?) ORDER BY id",