Support encrypting secrets with kms

[alexppg]

Is your feature request related to a problem? Please describe.
When using a microservice, you usually need to set passwords for a database, for example. It would be useful to be able to encrypt it for security reasons. It might support many backends, but the first one may be used with AWS kms.
Describe the solution you'd like
Similar to this: https://github.com/zalando/spring-cloud-config-aws-kms#usage

[avara1986]

Inspired by this article, I added a agnostic method to encrypt the configuration without vendor locking. Maybe as first step it's ok, but, could be better expand this functionality with AWS KMS and GCP KMS? Anyone knows if with a AES it's OK or need more secure methods?

[alexppg]

It is good for this purpose. For this approach I think it would be nice to have very clear documentation on how to handle the key, since the operator will be the responsible to deploy them to the infrastructure and make sure that is not accessible by any bad actor.