fix(esp_http_server): Add support for custom HTTP status codes

Closes https://github.com/espressif/esp-idf/issues/12399

components/esp_http_server/include/esp_http_server.h

@@ -1293,6 +1293,30 @@ esp_err_t httpd_resp_set_hdr(httpd_req_t *r, const char *field, const char *valu
  */
 esp_err_t httpd_resp_send_err(httpd_req_t *req, httpd_err_code_t error, const char *msg);
 
+/**
+ * @brief   For sending out custom error code in response to HTTP request.
+ *
+ * @note
+ *  - This API is supposed to be called only from the context of
+ *    a URI handler where httpd_req_t* request pointer is valid.
+ *  - Once this API is called, all request headers are purged, so
+ *    request headers need be copied into separate buffers if
+ *    they are required later.
+ *  - If you wish to send additional data in the body of the
+ *    response, please use the lower-level functions directly.
+ *
+ * @param[in] req     Pointer to the HTTP request for which the response needs to be sent
+ * @param[in] status  Error status to send
+ * @param[in] msg     Error message string
+ *
+ * @return
+ *  - ESP_OK : On successfully sending the response packet
+ *  - ESP_ERR_INVALID_ARG : Null arguments
+ *  - ESP_ERR_HTTPD_RESP_SEND   : Error in raw send
+ *  - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer
+ */
+esp_err_t httpd_resp_send_custom_err(httpd_req_t *req, const char *status, const char *msg);
+
 /**
  * @brief   Helper function for HTTP 404
  *