Environment Variables
Deribit.new() reads these when client_id/client_secret aren't passed directly.
DERIBIT_CLIENT_ID=
DERIBIT_CLIENT_SECRET=Deribit.new(testnet=True) reads the TEST_-prefixed pair instead:
TEST_DERIBIT_CLIENT_ID=
TEST_DERIBIT_CLIENT_SECRET=Neither pair is read for a Deribit.new(public=True) client — public methods and public
channel subscriptions need no credentials at all.