AP_DDS: add param DDS_DOMAIN_ID

- Require reboot.
- Set DDS_DOMAIN_ID range: 0 to 232..

Signed-off-by: Rhys Mainwaring <rhys.mainwaring@me.com>

libraries/AP_DDS/AP_DDS_Client.cpp

@@ -74,6 +74,14 @@ const AP_Param::GroupInfo AP_DDS_Client::var_info[] {
 
 #endif
 
+    // @Param: _DOMAIN_ID
+    // @DisplayName: DDS DOMAIN ID
+    // @Description: Set the ROS_DOMAIN_ID
+    // @Range: 0 232
+    // @RebootRequired: True
+    // @User: Standard
+    AP_GROUPINFO("_DOMAIN_ID", 4, AP_DDS_Client, domain_id, 0),
+
     AP_GROUPEND
 };
 
@@ -819,9 +827,8 @@ bool AP_DDS_Client::create()
         .type = UXR_PARTICIPANT_ID
     };
     const char* participant_name = "ardupilot_dds";
-    const uint16_t domain_id = 0;
     const auto participant_req_id = uxr_buffer_create_participant_bin(&session, reliable_out, participant_id,
-                                    domain_id, participant_name, UXR_REPLACE);
+                                    static_cast<uint16_t>(domain_id), participant_name, UXR_REPLACE);
 
     //Participant requests
     constexpr uint8_t nRequestsParticipant = 1;

libraries/AP_DDS/AP_DDS_Client.h

@@ -213,6 +213,9 @@ public:
     //! @brief Parameter storage
     static const struct AP_Param::GroupInfo var_info[];
 
+    //! @brief ROS_DOMAIN_ID
+    AP_Int32 domain_id;
+
     //! @brief Enum used to mark a topic as a data reader or writer
     enum class Topic_rw : uint8_t {
         DataReader = 0,