httpd_query_key_value() function

- ESP_OK : Key is found in the URL query string and copied to buffer - ESP_ERR_NOT_FOUND : Key not found - ESP_ERR_INVALID_ARG : Null arguments - ESP_ERR_HTTPD_RESULT_TRUNC : Value string truncated

- The components of URL query string (keys and values) are not URLdecoded. The user must check for 'Content-Type' field in the request headers and then depending upon the specified encoding (URLencoded or otherwise) apply the appropriate decoding algorithm. - If actual value size is greater than val_size, then the value is truncated, accompanied by truncation error as return value.