Automate setting up Duo Workflow Service in GDK

What does this merge request do and why?

Automate setting up Duo Workflow in GDK

As part of gitlab-org/duo-workflow/duo-workflow-service#55 (moved) we want to add automation that configures a Duo Workflow Service to simplify developer onboarding.

How to set up and validate locally

1. Run the instructions added in this MR
2. Get a personal access token from your GDK instance
3. curl -H "Private-Token: $GDK_TOKEN" -X POST 'http://gdk.test:3000/api/v4/ai/duo_workflows/direct_access' -i
4. That should return a duo_workflow_service.token indicating that it managed to call the Duo Workflow Service and generate a token for usage so the configuration is working

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.

Closes #55 (closed)