Is your feature request related to a problem? Please describe. I can not find the document or use case how to use AWS ECR as private registry.

Describe the solution you'd like we can run aws ecr get-login-password to get the authorization token and config the registry like below to deploy cf. But the token is only valid for 12 hours.

system_registry:
  add_image_pull_secrets: true
  hostname: https://${ecr_hostname}
  username: AWS
  password: ${ecr_token}

doc mentioning the expiration: https://docs.aws.amazon.com/cli/latest/reference/ecr/get-login-password.html

Describe alternatives you've considered It would be useful to suggest how to use ecr as private registry or is it an option?

Related to #345