fix: pubrel message resending when pubcomp not received

For the case when pubcomp wasn't received we should retry sending
pubrel.

Author: euripedesrocha

mqtt_client.c

@@ -1550,6 +1550,32 @@ static esp_err_t mqtt_resend_queued(esp_mqtt_client_handle_t client, outbox_item
     return ESP_OK;
 }
 
+static esp_err_t mqtt_resend_pubrel(esp_mqtt_client_handle_t client, outbox_item_handle_t item)
+{
+    client->mqtt_state.connection.outbound_message.data = outbox_item_get_data(item, &client->mqtt_state.connection.outbound_message.length, &client->mqtt_state.pending_msg_id,
+            &client->mqtt_state.pending_msg_type, &client->mqtt_state.pending_publish_qos);
+        if (client->mqtt_state.connection.information.protocol_ver == MQTT_PROTOCOL_V_5) {
+#ifdef MQTT_PROTOCOL_5
+            ESP_LOGI(TAG, "MQTT_MSG_TYPE_PUBREC return code is %d", mqtt5_msg_get_reason_code(client->mqtt_state.in_buffer, client->mqtt_state.in_buffer_read_len));
+            mqtt5_msg_pubrel(&client->mqtt_state.connection, client->mqtt_state.pending_msg_id);
+#endif
+        } else {
+            mqtt_msg_pubrel(&client->mqtt_state.connection, client->mqtt_state.pending_msg_id);
+        }
+        if (client->mqtt_state.connection.outbound_message.length == 0) {
+            ESP_LOGE(TAG, "Publish response message PUBREL cannot be created");
+            return ESP_FAIL;
+        }
+
+    if (esp_mqtt_write(client) != ESP_OK) {
+        ESP_LOGE(TAG, "Error to resend data ");
+        esp_mqtt_abort_connection(client);
+        return ESP_FAIL;
+    }
+
+    return ESP_OK;
+}
+
 static void mqtt_delete_expired_messages(esp_mqtt_client_handle_t client)
 {
     // Delete message after OUTBOX_EXPIRED_TIMEOUT_MS milliseconds
@@ -1723,6 +1749,16 @@ static void esp_mqtt_task(void *pv)
                         if (client->mqtt_state.connection.information.protocol_ver == MQTT_PROTOCOL_V_5) {
                             esp_mqtt5_increment_packet_counter(client);
                         }
+#endif
+                    }
+                }
+                item = outbox_dequeue(client->outbox, ACKNOWLEDGED, &msg_tick);
+                if (item && (last_retransmit - msg_tick > client->config->message_retransmit_timeout))  {
+                    if (mqtt_resend_pubrel(client, item) == ESP_OK) {
+#ifdef MQTT_PROTOCOL_5
+                        if (client->mqtt_state.connection.information.protocol_ver == MQTT_PROTOCOL_V_5) {
+                            esp_mqtt5_increment_packet_counter(client);
+                        }
 #endif
                     }
                 }