Add set_device_class API to change active device class

This API can be used to runtime change device class.

Please note that only class A and C are supported at the moment.
Trying to set class B will return LORAWAN_STATUS_UNSUPPORTED.

Fix set_device_class documentation

fix documentation

features/lorawan/LoRaWANBase.h

@@ -331,6 +331,18 @@ public:
      *                          callbacks.
      */
     virtual lorawan_status_t add_app_callbacks(lorawan_app_callbacks_t *callbacks) = 0;
+
+    /** Change device class
+     *
+     * Change current device class.
+     *
+     * @param    device_class   The device class
+     *
+     * @return                  LORAWAN_STATUS_OK on success,
+     *                          LORAWAN_STATUS_UNSUPPORTED is requested class is not supported,
+     *                          or other negative error code if request failed.
+     */
+    virtual lorawan_status_t set_device_class(const device_class_t device_class) = 0;
 };
 
 #endif /* LORAWAN_BASE_H_ */

features/lorawan/LoRaWANInterface.cpp

@@ -124,3 +124,8 @@ lorawan_status_t LoRaWANInterface::add_app_callbacks(lorawan_app_callbacks_t *ca
 {
     return stk_obj().set_lora_callbacks(callbacks);
 }
+
+lorawan_status_t LoRaWANInterface::set_device_class(const device_class_t device_class)
+{
+    return stk_obj().set_device_class(device_class);
+}

features/lorawan/LoRaWANInterface.h

@@ -428,6 +428,18 @@ public:
        *                          callbacks.
        */
     virtual lorawan_status_t add_app_callbacks(lorawan_app_callbacks_t *callbacks);
+
+    /** Change device class
+     *
+     * Change current device class.
+     *
+     * @param    device_class   The device class
+     *
+     * @return                  LORAWAN_STATUS_OK on success,
+     *                          LORAWAN_STATUS_UNSUPPORTED is requested class is not supported,
+     *                          or other negative error code if request failed.
+     */
+    virtual lorawan_status_t set_device_class(const device_class_t device_class);
 };
 
 #endif /* LORAWANINTERFACE_H_ */

features/lorawan/LoRaWANStack.cpp

@@ -1093,6 +1093,14 @@ lorawan_status_t LoRaWANStack::shutdown()
     return lora_state_machine(DEVICE_STATE_SHUTDOWN);
 }
 
+lorawan_status_t LoRaWANStack::set_device_class(const device_class_t device_class)
+{
+    loramac_mib_req_confirm_t mib_req;
+    mib_req.type = MIB_DEVICE_CLASS;
+    mib_req.param.dev_class = device_class;
+    return mib_set_request(&mib_req);
+}
+
 lorawan_status_t LoRaWANStack::lora_state_machine(device_states_t new_state)
 {
     loramac_mib_req_confirm_t mib_req;

features/lorawan/LoRaWANStack.h

@@ -360,6 +360,18 @@ public:
      */
     lorawan_status_t shutdown();
 
+    /** Change device class
+     *
+     * Change current device class.
+     *
+     * @param    device_class   The device class
+     *
+     * @return                  LORAWAN_STATUS_OK on success,
+     *                          LORAWAN_STATUS_UNSUPPORTED is requested class is not supported,
+     *                          or other negative error code if request failed.
+     */
+    lorawan_status_t set_device_class(const device_class_t device_class);
+
 private:
     LoRaWANStack();
     ~LoRaWANStack();

features/lorawan/lorastack/mac/LoRaMacMib.cpp

@@ -59,6 +59,7 @@ lorawan_status_t LoRaMacMib::set_request(loramac_mib_req_confirm_t *mibSet,
                     break;
                 }
                 case CLASS_B: {
+                    status = LORAWAN_STATUS_UNSUPPORTED;
                     break;
                 }
                 case CLASS_C: {