Support env in CredentialProviderConfig

[samjo-nyang]

What I'd like:
Hi, I'd like to add some custom environment variables to the credential provider config, such as

[settings.kubernetes.credential-providers.samjo-credential-provider]
enabled = true
cache-duration = "30m"
image-patterns = ["samjo.private.registry"]

[settings.kubernetes.credential-providers.samjo-credential-provider.env]
my-env = "1"

and it transforms into the following.

apiVersion: kubelet.config.k8s.io/v1alpha1
kind: CredentialProviderConfig
providers:
  - name: samjo-credential-provider
    matchImages:
      - "samjo.private.registry"
    defaultCacheDuration: "30m"
    apiVersion: credentialprovider.kubelet.k8s.io/v1alpha1
    env:
      - name: MY_ENV
        value: "1"

Also, I have a question of the following line - how does this work?
https://github.com/bottlerocket-os/bottlerocket/blame/develop/packages/kubernetes-1.24/credential-provider-config-yaml#L18

Since the line is in the "#each" context on line 5, should it be ../settings.aws.profile?

Any alternatives you've considered: (nothing)

[stmcginnis]

Regarding this part:

Also, I have a question of the following line - how does this work?

These don't end up being relative references, but are actually resolved to objects. So inside an #each block you can refer to the currently iterating item using this, but you can also refer to specific settings objects as is being done with the settings.aws.profile piece. Now I see what you were saying! Luckily that's been fixed.

Just to make sure I understand the background of the request - you're looking at adding another credential provider, but this provider has additional settings that would need to be passed in via environment variables, correct?

If so, it shouldn't be too difficult to extend the CredentialProvider struct that defines those settings to include an optional set of values. Something like:

# Probably define a new struct to simplify the Vec<HashMap<String, String>> type
env: Vec<HashMap<String, String>>,

Then in the templates there would need to be an #each loop through each of the env values to populate them in the CredentialProviderConfig settings.

I can't give any kind of timeline on when someone on the team here could get to it, but contributions definitely welcome if you want to propose this addition. :)