feat(example): Added DNS over HTTPS (DoH) example

examples/protocols/dns_over_https/components/time_sync/include/time_sync.h

@@ -0,0 +1,46 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Update system time from NVS or SNTP if not available.
+ *
+ * This function retrieves the stored system time from NVS. If the time is not found,
+ * it synchronizes with the SNTP server and updates the time in NVS.
+ *
+ * @return esp_err_t ESP_OK on success, ESP_FAIL on failure.
+ */
+esp_err_t update_time_from_nvs(void);
+
+/**
+ * @brief Fetch the current system time and store it in NVS.
+ *
+ * This function initializes SNTP, retrieves the current system time, and stores
+ * it in Non-Volatile Storage (NVS). In case of failure, an error message is logged.
+ *
+ * @param[in] args Unused argument placeholder.
+ * @return esp_err_t ESP_OK on success, ESP_FAIL on failure.
+ */
+esp_err_t fetch_and_store_time_in_nvs(void*);
+
+/**
+ * @brief Sets up periodic time updates.
+ *
+ * If the reset reason is power-on, this function updates the system time from NVS.
+ * It also creates a periodic timer to regularly fetch and store the time in NVS
+ * using `fetch_and_store_time_in_nvs` as the callback.
+ *
+ * @return void
+ */
+void setup_periodic_time_updates(void);
+
+#ifdef __cplusplus
+}
+#endif