Feature: Support workload identity federation

[jaredfholgate]

This PR is to add support for Workload Identity Federation (OIDC) in the Terraform Task.

The intention is that this will be a non-breaking change, it will simply identify the authentication scheme and setup the provider accordingly.

Testing Evidence:

In order to run this test, the following steps were followed:

1. Compiled and packaged the extension as per the steps HERE.
2. Removed the public extension from the organisation.
3. Published the extension to the market place, shared it to the organisation and installed it in the organisation.
4. Deployed the Service Connection, Managed Identity, etc using this example code: https://github.com/Azure-Samples/azure-devops-terraform-oidc-ci-cd
5. Updated the oidc.yml pipeline to include the Terraform task steps (see below).
6. Ran the pipeline.

Pipeline Code

Test Extension

Service Connection

Terraform Init

Terraform Apply

[jaredfholgate]

@mericstam Just as a heads up on what has been done in this PR:

• Added the new functionality to enable WorkloadIdentityFederation authentication schemes to the V4 task.
• Refactored the code slightly to support async / await for the command.
• Got the unit tests working.
• Got debugging working with the unit tests.
• Fixed the existing unit tests that appeared to be broken.
• Added new unit tests for the new functionality.

In terms of what needs to happen next:

• I need to be able to deploy the task and test it end to end, as I am unable to test the token generation outside of a pipeline.
• I could get the unit tests working in the pipeline if desired, but would need access to the Azure DevOps instance.

[jaredfholgate]

Closing this PR in favour of https://github.com/microsoft/azure-pipelines-terraform/pull/176 which uses a local branch instead of a Fork.

[jaredfholgate]

Closing this PR in favour of https://github.com/microsoft/azure-pipelines-terraform/pull/176 which uses a local branch instead of a Fork.