LiveKit key file holding one or multiple application secrets. Use livekit-server generate-keys to generate a random key name and secret.
The file should have the format <keyname>: <secret>. Example: lk-jwt-service: f6lQGaHtM5HfgZjIcec3cOCRfiDqIine4CpZZnqdT5cE
Individual key/secret pairs need to be passed to clients to connect to this instance.