httpd_req_get_url_query_str() function

- ESP_OK : Query is found in the request URL and copied to buffer - ESP_FAIL : uri is empty - ESP_ERR_NOT_FOUND : Query not found - ESP_ERR_INVALID_ARG : Null arguments - ESP_ERR_HTTPD_INVALID_REQ : Invalid HTTP request pointer - ESP_ERR_HTTPD_RESULT_TRUNC : Query string truncated

- Presently, the user can fetch the full URL query string, but decoding will have to be performed by the user. Request headers can be read using httpd_req_get_hdr_value_str() to know the 'Content-Type' (eg. Content-Type: application/x-www-form-urlencoded) and then the appropriate decoding algorithm needs to be applied. - This API is supposed to be called only from the context of a URI handler where httpd_req_t* request pointer is valid - If output size is greater than input, then the value is truncated, accompanied by truncation error as return value - Prior to calling this function, one can use httpd_req_get_url_query_len() to know the query string length beforehand and hence allocate the buffer of right size (usually query string length + 1 for null termination) for storing the query string