feat: added support for custom tags

[pcanilho]

Goal

This PR is aimed at adding support for publishing multiple image tags. This makes use of the existing feature-set provided by upstream ko-build/ko through the usage of the --tags flag.
cf. https://github.com/ko-build/ko/blob/0dcace336cc5f723150d77487dbaf56f849cc361/docs/reference/ko_build.md?plain=1#L62

By adding this functionality one is then able to avoid having to collide with an existing stable tag which is always named latest. This also opens the door for the usage of semver.

What changed?

• Added an optional tags schema field that takes a list of strings. If not provided, backwards compatibility is maintained by defaulting to the usage of the latest tag.
• Added new test suite TestAccResourceKoBuild_Tags to assert that new functionality works as expected and backwards compatibility is maintained.

Tests

Example usage

resource "ko_build" "this" {
  sbom        = "<your_sbom>"
  tags        = ["develop"]
  importpath  = "<your_importpath>"
  repo        = "<your_repo>"
  working_dir = "<your_work_dir>"
}

[imjasonh]

This looks good! Can you add a simple test that creating a resource with tags produces an image with those tags?

[pcanilho]

This looks good! Can you add a simple test that creating a resource with tags produces an image with those tags?

@imjasonh I have added a new test suite called TestAccResourceKoBuild_Tags that I believe covers the changes proposed in this PR. I have retroactively updated the first comment. :-)