Joining a Wi-Fi network from an ESP32 in station mode, handling connection events and reading RSSI without blocking

Required by

• Calling a REST API from an ESP32 with JSON bodies, and telling safe and idempotent methods apart required
• Getting Wi-Fi credentials onto a device without compiling them in (SoftAP portal, BLE, serial), storing them in NVS, and resetting them required
• Joining Wi-Fi and getting an address from Rust with esp-radio and embassy-net, and judging the maturity of Rust MQTT required
• Reasoning about Wi-Fi range, interference, coexistence and power-save modes on a battery device required
• Serving a local status page and a small JSON endpoint from an ESP32 without blocking the firmware required