See https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/ug_fw_update.html#ug-fw-update-keys
for the possible methods to generate the firmware signing keys.

*** DO NOT PUSH THE KEYS TO GIT ***

Only the key 'development_private.pem' key can be stored in Git. Use it only for
development, *** NEVER *** for production.