Add new slave_wifi_rest_api example: REST Wi-Fi control based on original slave (IDFGH-16209)

components/eppp_link/examples/slave_wifi_rest_api/CMakeLists.txt

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+# The following five lines of boilerplate have to be in your project's
+# CMakeLists in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.16)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(pppos_slave)

components/eppp_link/examples/slave_wifi_rest_api/README.md

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+# ESP32 [eppp\_link/slave](../slave/) based Example – Modifications and REST Wi-Fi Control
+
+[See the original example here](../slave/)
+
+This document describes the key modifications and usage instructions for the enhanced [slave](../slave/) example, enabling REST-based Wi-Fi configuration and monitoring.
+
+---
+
+## Overview
+
+This version extends the original [slave](../slave/) PPP example with a full-featured REST API for Wi-Fi management. All new functionality is backward compatible; Wi-Fi can still be set via Kconfig, but runtime control is now possible from your browser or scripts.
+
+---
+
+## Key Changes
+
+### 1. REST API for Wi-Fi
+
+* Added HTTP server (`esp_http_server`) and JSON parsing (`cJSON`).
+* REST endpoints:
+
+  * `GET /wifi/status` — current status (connected/disconnected, SSID, RSSI).
+  * `GET /wifi/scan` — scan available Wi-Fi networks.
+  * `POST /wifi/connect` — connect to network (JSON: `{ "ssid": ..., "password": ... }`).
+  * `POST /wifi/disconnect` — disconnect from Wi-Fi.
+  * `OPTIONS /*` — CORS preflight for all URIs.
+
+### 2. Dynamic Wi-Fi Reconfiguration
+
+* Supports runtime change of Wi-Fi credentials without reboot or reflash.
+* Connect/disconnect sequence is carefully synchronized using event groups for stability.
+* If no default SSID is set, the device waits for configuration via REST.
+
+### 3. Event Management Improvements
+
+* Uses EventGroup bits to distinguish connection, failure, and disconnection events.
+* Manual reconnect flag to suppress auto-retry logic during REST-initiated reconnects.
+
+### 4. CORS Support
+
+* All REST responses include `Access-Control-Allow-Origin: *` for easy browser access.
+
+---
+
+## How to Use
+
+### Build & Flash
+
+* Add `esp_http_server` and `cJSON` to your project.
+* Build and flash as usual with ESP-IDF.
+
+### Default Startup
+
+* If Wi-Fi SSID and password are set in `sdkconfig`, ESP32 tries to connect at startup.
+* If no SSID set, device waits for Wi-Fi config from REST client.
+
+### REST API Usage
+
+Interact from browser, curl, or your own UI:
+
+* **Get status:**
+
+  ```bash
+  curl http://<esp32_ip>/wifi/status
+  ```
+* **Scan networks:**
+
+  ```bash
+  curl http://<esp32_ip>/wifi/scan
+  ```
+* **Connect:**
+
+  ```bash
+  curl -X POST http://<esp32_ip>/wifi/connect -H "Content-Type: application/json" -d '{"ssid":"YOUR_SSID","password":"YOUR_PASS"}'
+  ```
+* **Disconnect:**
+
+  ```bash
+  curl -X POST http://<esp32_ip>/wifi/disconnect
+  ```
+
+> See [Web panel](webPanel/) for a ready-to-use web UI!
+
+---
+
+## Implementation Notes
+
+* All Wi-Fi connect/disconnect operations are handled asynchronously and robustly.
+* If REST connect/disconnect is called in the middle of another operation, API will wait for proper sequence.
+* All actions are CORS-enabled for direct use from web apps.
+* Wi-Fi scan returns SSID, RSSI, and auth mode for each visible AP (max 16).
+
+---
+
+## Example: Integrating with Your UI
+
+You can use the provided web UI ([See documentation for the web panel](webPanel/README.md)
+) or integrate these endpoints into any admin dashboard, mobile app, or automation script.
+
+---
+
+## Credits
+
+* Enhanced by \glarionenko, \2025
+* Based on original code © 2023-2025 Espressif Systems (Shanghai) CO LTD

components/eppp_link/examples/slave_wifi_rest_api/main/CMakeLists.txt

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+if(CONFIG_EXAMPLE_WIFI_OVER_EPPP_CHANNEL)
+    set(wifi_over_channels channel_wifi_station.c)
+endif()
+
+idf_component_register(
+    SRCS eppp_slave.c
+         ${wifi_over_channels}
+    INCLUDE_DIRS "."
+    REQUIRES json esp_wifi nvs_flash esp_http_server
+)

components/eppp_link/examples/slave_wifi_rest_api/main/Kconfig.projbuild

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+menu "Example Configuration"
+
+    config ESP_WIFI_SSID
+        string "WiFi SSID"
+        default "myssid"
+        help
+            SSID (network name) for the example to connect to.
+
+    config ESP_WIFI_PASSWORD
+        string "WiFi Password"
+        default "mypassword"
+        help
+            WiFi password (WPA or WPA2) for the example to use.
+
+    config ESP_MAXIMUM_RETRY
+        int "Maximum retry"
+        default 5
+        help
+            Set the Maximum retry to avoid station reconnecting to the AP unlimited when the AP is really inexistent.
+
+    config EXAMPLE_SPI_HOST
+        int "SPI Host"
+        depends on EPPP_LINK_DEVICE_SPI
+        default 1
+        range 0 2
+        help
+            SPI host to use (SPI1_HOST=0, SPI2_HOST=1, SPI3_HOST=2).
+
+    config EXAMPLE_SPI_MOSI_PIN
+        int "MOSI Pin Number"
+        depends on EPPP_LINK_DEVICE_SPI
+        default 23
+        range 0 39
+        help
+            Pin number of SPI MOSI.
+
+    config EXAMPLE_SPI_MISO_PIN
+        int "MISO Pin Number"
+        depends on EPPP_LINK_DEVICE_SPI
+        default 19
+        range 0 39
+        help
+            Pin number of SPI MISO.
+
+    config EXAMPLE_SPI_SCLK_PIN
+        int "SCLK Pin Number"
+        depends on EPPP_LINK_DEVICE_SPI
+        default 18
+        range 0 39
+        help
+            Pin number of SPI SCLK.
+
+    config EXAMPLE_SPI_CS_PIN
+        int "CS Pin Number"
+        depends on EPPP_LINK_DEVICE_SPI
+        default 5
+        range 0 39
+        help
+            Pin number of SPI CS.
+
+    config EXAMPLE_SPI_INTR_PIN
+        int "Interrupt Pin Number"
+        depends on EPPP_LINK_DEVICE_SPI
+        default 17
+        range 0 39
+        help
+            Pin number of SPI interrupt.
+
+    config EXAMPLE_SPI_FREQUENCY
+        int "SPI Frequency (Hz)"
+        depends on EPPP_LINK_DEVICE_SPI
+        default 1000000
+        range 100000 80000000
+        help
+            SPI frequency in Hz.
+
+    config EXAMPLE_UART_TX_PIN
+        int "TXD Pin Number"
+        depends on EPPP_LINK_DEVICE_UART
+        default 18
+        range 0 31
+        help
+            Pin number of UART TX.
+
+    config EXAMPLE_UART_RX_PIN
+        int "RXD Pin Number"
+        depends on EPPP_LINK_DEVICE_UART
+        default 17
+        range 0 31
+        help
+            Pin number of UART RX.
+
+    config EXAMPLE_UART_BAUDRATE
+        int "Baudrate"
+        depends on EPPP_LINK_DEVICE_UART
+        default 921600
+        range 0 4000000
+        help
+            Baudrate used by the PPP over UART
+
+    config EXAMPLE_WIFI_OVER_EPPP_CHANNEL
+        bool "Use WiFi over EPPP channel"
+        default n
+        depends on EPPP_LINK_CHANNELS_SUPPORT
+        help
+            Enable this option to use WiFi over EPPP channel.
+            If this option is enabled, the example will only start the Wi-Fi driver,
+            but the Wi-Fi netif will reside on client's end and will channel
+            the Rx and Tx data via EPPP channels.
+
+endmenu