Add values settings for using a shared credentials file #1330
Description
Is your feature request related to a problem?
In the documentation on using a shared credentials file there are instructions for mounting a secret containing AWS credentials on the pod for an ACK controller, so it can use those credentials. However, for the RDS controller there is no way to specify which secret to use when following the installation instructions with Helm.
Describe the solution you'd like
Add new values settings that can be used to specify that secret. See proposal in aws-controllers-k8s/rds-controller#86
Describe alternatives you've considered
Using env variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY, which is not recommended by the documentation