A secrets management service would be most convenient. Documentation makes them easy to set up without having to build anything extra yourself. A secrets manager like Doppler (https://Doppler.com) or AWS Secrets Manager (https://aws.amazon.com/secrets-manager/) has the advantage of protecting your secrets in a secure place and the advantage of minimizing exposure of those secrets - even to your own developers. That way, you don't end up with a data breach that could have easily been avoided. These types of leaks can cost companies everything and are becoming way more common.