esp_http_server: Provide apps an option to let http_server ignore sess_ctx changes

By default, if a URI handler changes the http session context,
the webserver internally clears the older context after the handler
returns. However, if applications want to change this behavior and
manage the allocation/de-allocation/freeing themselves and let the
server handle only the "socket close" case, this commit provides such
an option.

components/esp_http_server/include/esp_http_server.h

@@ -362,6 +362,18 @@ typedef struct httpd_req {
      * function for freeing the session context, please specify that here.
      */
     httpd_free_ctx_fn_t free_ctx;
+
+    /**
+     * Flag indicating if Session Context changes should be ignored
+     *
+     * By default, if you change the sess_ctx in some URI handler, the http server
+     * will internally free the earlier context (if non NULL), after the URI handler
+     * returns. If you want to manage the allocation/reallocation/freeing of
+     * sess_ctx yourself, set this flag to true, so that the server will not
+     * perform any checks on it. The context will be cleared by the server
+     * (by calling free_ctx or free()) only if the socket gets closed.
+     */
+    bool ignore_sess_ctx_changes;
 } httpd_req_t;
 
 /**