feature: Added user callback for esp_https_server

- Can be used to get connection or client information (SSL context)
- E.g. Client certificate, Socket FD, Connection state, etc.
- Added example callback for getting client certificate information in 'https_server/simple' example

Closes https://github.com/espressif/esp-idf/issues/7479

components/esp_https_server/src/https_server.c

@@ -15,6 +15,7 @@ const static char *TAG = "esp_https_server";
 typedef struct httpd_ssl_ctx {
     esp_tls_cfg_server_t *tls_cfg;
     httpd_open_func_t open_fn;
+    esp_https_server_user_cb *user_cb;
 } httpd_ssl_ctx_t;
 
 /**
@@ -119,6 +120,13 @@ static esp_err_t httpd_ssl_open(httpd_handle_t server, int sockfd)
     if (global_ctx->open_fn) {
         (global_ctx->open_fn)(server, sockfd);
     }
+
+    if (global_ctx->user_cb) {
+        esp_https_server_user_cb_arg_t user_cb_data = {0};
+        user_cb_data.tls = tls;
+        (global_ctx->user_cb)((void *)&user_cb_data);
+    }
+
     return ESP_OK;
 fail:
     esp_tls_server_session_delete(tls);
@@ -172,6 +180,7 @@ static httpd_ssl_ctx_t *create_secure_context(const struct httpd_ssl_config *con
     }
 
     ssl_ctx->tls_cfg = cfg;
+    ssl_ctx->user_cb = config->user_cb;
 /* cacert = CA which signs client cert, or client cert itself , which is mapped to client_verify_cert_pem */
     if(config->client_verify_cert_pem != NULL) {
         cfg->cacert_buf = (unsigned char *)malloc(config->client_verify_cert_len);