Contribution description

This PR simplifies the definition of the option to use dynamic SSIDs for the SoftAP, especially with regard to the migration to Kconfig.

The semantics of defining a separate SSID prefix string that overrides the already defined SSID and enables the dynamic SSID generation with that prefix exactly when and only when it is set, made the handling of the parameter definition unnecessarily difficult and hard to understand.

Defining a boolean option that just enables the dynamic SSID generation, which then simply reuses the defined SSID as a prefix, makes it much more understandable and easier to handle, especially with respect to Kconfig.

This PR removes the configuration parameter ESP_WIFI_PREFIX and introduces the boolean configuration parameter ESP_WIFI_SSID_DYNAMIC which is defined as 0 by default. If set to 1, the already defined ESP_WIFI_SSID is used as prefix to generate a dynamic SSID by extending it with the MAC address of the SoftAP interface used, e.g.: RIOT_AP_aabbccddeeff

Testing procedure

Compile and flash test application

USEMODULE=esp_wifi_ap \
CFLAGS='-DESP_WIFI_SSID=\"MySSID\" -DESP_WIFI_PASS=\"MyPassphrase\" -DESP_WIFI_MAX_CONN=1'  \
make -C examples/gnrc_networking BOARD=esp32-wroom-32 flash

with and without -DESP_WIFI_SSID_DYNAMIC=1 in CFLAGS and use any WiFi device to check the used SSID.

Without -DESP_WIFI_SSID_DYNAMIC=1, the SSID of the SoftAP should be RIOT_AP, with -DESP_WIFI_SSID_DYNAMIC=1, the SSID of the SoftAP should be something like RIOT_AP_<mac>

Issues/PRs references