Is your feature request related to a problem? Please describe.
We have custom solution to read secrets from vault and provide it for the apps to use. I wanted to replace the image provided by vault that is used as init/sidecar container and use our own image. Our custom image requires few env variable to work.
Provide a way to pass env variables from mentioned application dc (annotations) to init/sidecar container env variable.

Describe the solution you'd like
extraEnvironmentVars option that is provided in application DC, make it available to init/sidecar as environment variable. I can then this option to inject my required variables to sidecar/init images.

If this change is provided I will be able to use vault agent in our organisation.