Add support for reading in credentials from env or file, so k8s secret can be used

[embroede]

https://kubernetes.io/docs/concepts/configuration/secret/

[embroede]

It would be ideal to have the ability to specify a file path or environment variable name in values.yaml for the Redis and MySQL credentials.

This would be a significant improvement over the current method where a password needs to be hard coded in values.yaml.

[jim3ma]

You can load secret file as you want by --set-file

helm install -h:

--set-file stringArray         set values from respective files specified via the command line (can specify multiple or separate values with commas: key1=path1,key2=path2)