Add no-code endpoint for fetching registry module variables.

[paladin-devops]

Description

This PR adds support to go-tfe for the HCP Terraform endpoint to retrieve a no-code module's variables.

Testing plan

1. Create a no-code module with at least one required input variable.
2. Get the ID of the no-code module.
   • expected format: nocode-abcdefgh12345678
3. Set the environment variable NO_CODE_MODULE_ID to be that ID.
4. Run go test -run TestRegistryNoCodeModule -v ./..., with the other necessary testing environment variables.

Test Output

=== RUN   TestRegistryNoCodeModulesReadVariables
--- PASS: TestRegistryNoCodeModulesReadVariables (7.94s)
=== RUN   TestRegistryNoCodeModulesReadVariables/happy_path
    --- PASS: TestRegistryNoCodeModulesReadVariables/happy_path (7.66s)
PASS

[paladin-devops]

I think this could be a bug in the unmarshaler implementation. In the case of the change in this PR, Items is a slice, and in the unmarshalResponse function, it should be handled by jsonapi.UnmarshalManyPayload. However, without the *Pagination field of this struct present (which should not actually be here, because the backend service doesn't actually return a *Pagination) in the response), the conditional here sends the request into the jsonapi handler UnmarshalPayload, which is documented to support "single request payloads only", leading an attempt to decode a slice to fail.

For now, just including the *Pagination field here is a workaround. But if this issue is fixed, then it can be removed (or if pagination is implemented on the backend, it should be kept).

[sebasslash]

This is a great callout, I'll create a ticket to look into this. 👍

[sebasslash]

One minor change to the changelog, a few extra comments and you're good to go :)

[sebasslash]

This is a great callout, I'll create a ticket to look into this. 👍

[sebasslash]

Let's add a GODOC comment here as well

[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.