Add private registry provider platform API

[annawinkler]

Description

This PR was broken out of this PR.

This PR adds support for the private registry provider platform API.

Testing plan

To test these changes locally, create a local go project, and in the go.mod include a line similar to the following:

replace github.com/hashicorp/go-tfe => /Users/YOURUSER/go/src/github.com/hashicorp/go-tfe

Then, for a registry provider platform, you can test:

• Create
• Delete
• Read
• List

External links

• Registry Providers API
• Private Registry Provider Requirements
• Private Provider Versions and Platforms API

Output from tests

Including output from tests may require access to a TFE instance. Ignore this section if you have no environment to test against.

$ TFE_ADDRESS="https://example" TFE_TOKEN="example" TF_ACC="1" go test ./... -v -tags=integration -run TestFunctionsAffectedByChange

...

---

• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1202295552965199