Support SOPS encrypted data for kustomize secretGenerator "envs" argument

[sobi3ch]

At the moment Flux supports secretGenerator with sops for literal and files attributes but not for envs. It would be great to keep only env files encrypted in flux repo and leave the rest to Flux.

Here is a tutorial how to use sops with manual kustomize build command (section: With .env files). Sops can easily encrypt and decrypt env files.