This is an ACME client for ESP (ESP32, etc) devices, so your IoT can fetch their own certificate for secure communication. ACME is a protocol (see RFC8555) for automatic certificate management. Sites such as letsencrypt.org allow you to obtain free (no charge) certificates in an automated way using the ACME protocol.
ESP-IDF captive portal component with Wi-Fi configuration, scanning, DNS hijacking, mDNS, and HTTP server. Directly usable as an API component for any ESP32 series.