Allow profiles to be specified

[asobrien]

It would be nice if the AWS profile that credentials should be sourced from could be
specified when using heptio-authenticator-aws. Of course, this can already be done
by using the AWS_PROFILE environment variable. However, adding profiles as an
explicit option would be useful when working with clusters across multiple AWS
accounts and allow seamless switching.

For example, if a --profile flag was supported then kubectl would not require the
AWS_PROFILE environment variable to be modified for each cluster/account. The
appropriate profile could be specified directly in the kubeconfig file, e.g.:

apiVersion: v1
clusters:
- cluster:
    server: ${server}
    certificate-authority-data: ${cert}
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: aws
  name: aws
current-context: aws
kind: Config
preferences: {}
users:
- name: aws
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1alpha1
      command: heptio-authenticator-aws
      args:
        - "token"
        - "-i"
        - "mycluster"
        - "-p"
        - "dev"

[christopherhein]

Hey @asobrien there is actually support for this built into the ExecCredentials flow…

Update your config to include:

env:
- name: AWS_PROFILE
   value: dev

more information - https://kubernetes.io/docs/reference/access-authn-authz/authentication/#client-go-credential-plugins#configuration

For the PR you submitted maybe we can make that to add documentation to how to configure this instead of adding the flag?

[asobrien]

Perfect, that'd work! I'll verify it works as expected and update the README and docs to specify that profiles can be specified via the env block.

[christopherhein]

Thanks! @asobrien