[TF-7941] Add support for Terraform Test

[aaabdelgany]

Description

This PR adds support for the new Terraform Test Runs API.

We can create new kinds of registry modules (branch-based), upload configuration versions against registry modules, and create, monitor, and cancel test runs.

Testing plan

I've ran numerous e2e tests manually using my local build of Terraform Core. You can see the PR in the Terraform repo that uses this to integrate the testing framework with TFC: hashicorp/terraform#33710

I've added integration tests for the new API calls in this PR as well, but they are unfortunately untestable at the moment as the test endpoints are protected by a feature flag while the testing framework is going through the Beta rollout. This means that organisations created newly within the testing framework don't have access to the test runs endpoint.

Testing output

I have executed the tests locally, by hacking the create organisation helper function to load an already whitelisted organisation from the staging environment instead of creating a new one and they've passed.

~/hashicorp/go-tfe (nexus/terraform_test_cli) > envchain go-tfe go test -run TestTestRuns -v ./...
?       github.com/hashicorp/go-tfe/examples/configuration_versions     [no test files]
?       github.com/hashicorp/go-tfe/examples/organizations      [no test files]
?       github.com/hashicorp/go-tfe/examples/registry_modules   [no test files]
?       github.com/hashicorp/go-tfe/examples/state_versions     [no test files]
?       github.com/hashicorp/go-tfe/examples/users      [no test files]
?       github.com/hashicorp/go-tfe/examples/workspaces [no test files]
?       github.com/hashicorp/go-tfe/mocks       [no test files]
=== RUN   TestTestRunsList
=== RUN   TestTestRunsList/without_list_options
=== RUN   TestTestRunsList/empty_list_options
=== RUN   TestTestRunsList/with_page_size
--- PASS: TestTestRunsList (5.82s)
    --- PASS: TestTestRunsList/without_list_options (0.23s)
    --- PASS: TestTestRunsList/empty_list_options (0.23s)
    --- PASS: TestTestRunsList/with_page_size (0.21s)
=== RUN   TestTestRunsRead
=== RUN   TestTestRunsRead/when_the_test_run_exists
=== RUN   TestTestRunsRead/when_the_test_run_does_not_exist
--- PASS: TestTestRunsRead (4.55s)
    --- PASS: TestTestRunsRead/when_the_test_run_exists (0.23s)
    --- PASS: TestTestRunsRead/when_the_test_run_does_not_exist (0.20s)
=== RUN   TestTestRunsCreate
=== RUN   TestTestRunsCreate/with_a_configuration_version
=== RUN   TestTestRunsCreate/without_a_configuration_version
=== RUN   TestTestRunsCreate/without_a_module
--- PASS: TestTestRunsCreate (4.09s)
    --- PASS: TestTestRunsCreate/with_a_configuration_version (0.29s)
    --- PASS: TestTestRunsCreate/without_a_configuration_version (0.00s)
    --- PASS: TestTestRunsCreate/without_a_module (0.00s)
=== RUN   TestTestRunsLogs
=== RUN   TestTestRunsLogs/when_the_log_exists
=== RUN   TestTestRunsLogs/when_the_log_does_not_exist
--- PASS: TestTestRunsLogs (11.90s)
    --- PASS: TestTestRunsLogs/when_the_log_exists (7.54s)
    --- PASS: TestTestRunsLogs/when_the_log_does_not_exist (0.21s)
=== RUN   TestTestRunsCancel
=== RUN   TestTestRunsCancel/when_the_run_exists
=== RUN   TestTestRunsCancel/when_the_run_does_not_exist
--- PASS: TestTestRunsCancel (4.63s)
    --- PASS: TestTestRunsCancel/when_the_run_exists (0.24s)
    --- PASS: TestTestRunsCancel/when_the_run_does_not_exist (0.21s)
PASS
ok      github.com/hashicorp/go-tfe     31.696s

[brandonc]

Looks highly idiomatic! Just a few minor concerns

[brandonc]

Organization could be nil here, causing a panic. You could check for this in TestRunCreateOptions valid

[liamcervante]

Done!

[brandonc]

I don't think this is being used

[liamcervante]

Removed!

[brandonc]

👍

[github-actions]

Reminder to the contributor that merged this PR: if your changes have added important functionality or fixed a relevant bug, open a follow-up PR to update CHANGELOG.md with a note on your changes.