feat: support for pinning docker digests by image config

[olblak]

Fix #1603

updatecli.yaml

# To compare the following digests with 
# https://github.com/updatecli/updatecli/pkgs/container/updatecli/139180422?tag=v0.64.1

sources:
  noarch:
    name: "Get Digest for docker image updatecli/updatecli:v0.64.1"
    kind: "dockerdigest"
    spec:
      image: "ghcr.io/updatecli/updatecli"
      tag: "v0.64.1"

  amd64:
    name: "Get Digest for docker image updatecli/updatecli:v0.64.1"
    kind: "dockerdigest"
    spec:
      image: "ghcr.io/updatecli/updatecli"
      tag: "v0.64.1"
      architecture: amd64

  arm64:
    name: "Get Digest for docker image updatecli/updatecli:v0.64.1"
    kind: "dockerdigest"
    spec:
      image: "ghcr.io/updatecli/updatecli"
      tag: "v0.64.1"
      architecture: arm64

Test

To test this pull request, you can run the following commands:

cd pkg/plugins/resources/dockerdigest/ 
go test

Additional Information

Tradeoff

Potential improvement