image-builder github action dry-run

[dekiel]

Description

Image builder supports push or pull_request_target events only. Because the workflow file is taken from base branch for these events, it makes difficult to test changes in workflows using image-builder reusable workflow and image-builder reusable workflow itself. To make testing easier an image-builder reusable workflow can have a dry-run input.

When dry-run is set to true, an image-builder would not call ADO API but print call parameters values only. Because there won't be a real call to ADO, an execution will not require ADO PAT and OIDC token. In dry-run mode image-builder reusable workflow will allow to be executed on pull_request event, allowing user to test changes in a workflow in a pull request.

When running in dry run mode, an image-builder reusable workflow should return as output relevant configuration and ado api calls parameters values used by the tool. This will allow testing the output against expected values.

Acceptance Criteria

• [ ] Developer can test GitHub workflow which uses image-builder reusable workflow on pull request
• [ ] The image-builder reusable workflow returns dry run output