Publish: Allow for qos=0 messages to be stored using esp_mqtt_client_enqueue()

The API presents a boolean parameter to control storing the qos=0
messages into the internal outbox

lib/include/mqtt_outbox.h

@@ -43,6 +43,7 @@ uint8_t *outbox_item_get_data(outbox_item_handle_t item,  size_t *len, uint16_t
 esp_err_t outbox_delete(outbox_handle_t outbox, int msg_id, int msg_type);
 esp_err_t outbox_delete_msgid(outbox_handle_t outbox, int msg_id);
 esp_err_t outbox_delete_msgtype(outbox_handle_t outbox, int msg_type);
+esp_err_t outbox_delete_item(outbox_handle_t outbox, outbox_item_handle_t item);
 int outbox_delete_expired(outbox_handle_t outbox, outbox_tick_t current_tick, outbox_tick_t timeout);
 /**
  * @brief Deletes single expired message returning it's message id

lib/mqtt_outbox.c

@@ -80,6 +80,20 @@ outbox_item_handle_t outbox_dequeue(outbox_handle_t outbox, pending_state_t pend
     return NULL;
 }
 
+esp_err_t outbox_delete_item(outbox_handle_t outbox, outbox_item_handle_t item_to_delete)
+{
+    outbox_item_handle_t item;
+    STAILQ_FOREACH(item, outbox, next) {
+        if (item == item_to_delete) {
+            STAILQ_REMOVE(outbox, item, outbox_item, next);
+            free(item->buffer);
+            free(item);
+            return ESP_OK;
+        }
+    }
+    return ESP_FAIL;
+}
+
 uint8_t *outbox_item_get_data(outbox_item_handle_t item,  size_t *len, uint16_t *msg_id, int *msg_type, int *qos)
 {
     if (item) {