Write end-to-end test for branch planner

[yiannistri]

Follow-up from #665

This should run in CI under the e2e workflow as a separate job. The majority of the test execution code should be invoked as a make target to facilitate local execution.

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User Story:

As a Terraform Controller developer, I'd like to have an end-to-end test for the branch planner component, so that I can ensure its proper functionality and reduce the chances of introducing regression issues.

Acceptance Criteria:

• [ ] Create an end-to-end test for the branch planner component that covers its main functionalities.
• [ ] Test should be runnable in CI under the e2e workflow as a separate job.
• [ ] The majority of the test execution code is invoked as a make target, allowing for easy local execution.

[yiannistri]

Waiting for corp-it to get some credentials that we can use to setup Terraform.

[LappleApple]

@yiannistri How far have you gotten?

Would be a requirement before we release v0.16.0 TF Controller

[LappleApple]

Yiannis wants to deploy branch-planner to staging and use the knowledge gathered there to write the e2e. But it's hard to track, manage infra in stg with real tokens. Yiannis has opened some issues for Ciaran he'll follow up on.