fix: update validation for image builder workflow type

[stefanfreitag]

Description

The documentation of the resource ami_imagebuilder_workflow mentions for the argument type

Valid values: BUILD, TEST, DISTRIBUTION.

Image Builder handles the workflow type DISTRIBUTION, it cannot be configured by users. When trying to do so, for example using the code snippet provided as part of #39785

resource aws_imagebuilder_workflow codebuild-projects {
  name = "CodeBuildProjectsDistributionWorkflow"
  version = "1.0.0"
  type = "DISTRIBUTION"
  data = file("${path.module}/codebuild-projects-distribution.workflow.yaml")
}

the API returns the error The value supplied for parameter 'type' is not valid. Custom distribution workflows are not supported.

This pull request is to update the documentation for the resource as well as the validation for the argument. Two points from my side:

• For the validation I was not sure on the correct approach: I changed ValidateDiagFunc to ValidateFunc, typically it should be the other, right? Feedback is appreciated.
• How would I test the change in the validation? At the moment we do not have a test for attribute type, but adding one would also not cover the change.

Relations

Closes #39785

References

Here I explained the current situation.

Output from Acceptance Testing

❯ make testacc TESTS=TestAccImageBuilderWorkflow PKG=imagebuilder
make: Verifying source code with gofmt...
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go1.23.2 test ./internal/service/imagebuilder/... -v -count 1 -parallel 20 -run='TestAccImageBuilderWorkflow'  -timeout 360m
2024/10/20 21:04:19 Initializing Terraform AWS Provider...
=== RUN   TestAccImageBuilderWorkflow_basic
=== PAUSE TestAccImageBuilderWorkflow_basic
=== RUN   TestAccImageBuilderWorkflow_disappears
=== PAUSE TestAccImageBuilderWorkflow_disappears
=== RUN   TestAccImageBuilderWorkflow_changeDescription
=== PAUSE TestAccImageBuilderWorkflow_changeDescription
=== RUN   TestAccImageBuilderWorkflow_description
=== PAUSE TestAccImageBuilderWorkflow_description
=== RUN   TestAccImageBuilderWorkflow_kmsKeyID
=== PAUSE TestAccImageBuilderWorkflow_kmsKeyID
=== RUN   TestAccImageBuilderWorkflow_tags
=== PAUSE TestAccImageBuilderWorkflow_tags
=== RUN   TestAccImageBuilderWorkflow_uri
=== PAUSE TestAccImageBuilderWorkflow_uri
=== CONT  TestAccImageBuilderWorkflow_basic
=== CONT  TestAccImageBuilderWorkflow_kmsKeyID
=== CONT  TestAccImageBuilderWorkflow_uri
=== CONT  TestAccImageBuilderWorkflow_tags
=== CONT  TestAccImageBuilderWorkflow_changeDescription
=== CONT  TestAccImageBuilderWorkflow_description
=== CONT  TestAccImageBuilderWorkflow_disappears
--- PASS: TestAccImageBuilderWorkflow_disappears (42.21s)
--- PASS: TestAccImageBuilderWorkflow_basic (47.48s)
--- PASS: TestAccImageBuilderWorkflow_changeDescription (47.56s)
--- PASS: TestAccImageBuilderWorkflow_description (47.66s)
--- PASS: TestAccImageBuilderWorkflow_kmsKeyID (49.77s)
--- PASS: TestAccImageBuilderWorkflow_uri (55.30s)
--- PASS: TestAccImageBuilderWorkflow_tags (85.21s)
PASS
ok      github.com/hashicorp/terraform-provider-aws/internal/service/imagebuilder       85.434s
...