Function esp_mqtt5_client_get_user_property 

pub unsafe extern "C" fn esp_mqtt5_client_get_user_property(
    user_property: *mut mqtt5_user_property_list_t,
    item: *mut esp_mqtt5_user_property_item_t,
    item_num: *mut u8,
) -> i32

@brief Get MQTT5 client user property

@param user_property user_property handle @param item point that store user property data @param item_num number of items in user property data

This API can use with esp_mqtt5_client_get_user_property_count to get list count of user property. And malloc number of count item array memory to store the user property data. Please DO NOT forget the item memory, key and value point in item memory when get user property data successfully.

@return ESP_ERR_NO_MEM if failed to allocate ESP_FAIL on fail ESP_OK on success