Fix: Support app auth and PAT via two provider instances

[MajorBreakfast]

Resolves #1537

---

Behavior

Before the change?

The following code errors if both GITHUB_APP_... and GITHUB_TOKEN env vars are set:

provider "github" { # Uses GITHUB_APP_... env vars
  app_auth {}
}

The error message looks like this:

│ Error: no decodeable PEM data found
│ 
│   with provider["registry.terraform.io/hashicorp/github"],
│   on main.tf line 1, in provider "github":
│    1: provider "github" {

After the change?

• app_auth {} block set => Provider uses the GITHUB_APP_... env vars (currently the case*), ignores GITHUB_TOKEN env var (new)
• app_auth {} block not set => Provider uses the GITHUB_TOKEN env var (currently the case*), ignores GITHUB_APP_... env vars (currently the case*)

Other information

---

Additional info

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Added the appropriate label for the given change

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes (Please add the Type: Breaking change label)
• No

If Yes, what's the impact:

• N/A

Pull request type

Please add the corresponding label for change this PR introduces:

• Bugfix: Type: Bug
• Feature/model/API additions: Type: Feature
• Updates to docs or samples: Type: Documentation
• Dependencies/code cleanup: Type: Maintenance

---

[kfcampbell]

This PR does not take into account your proposed alias keyword in #1537. Do you view this as a transitional step? Are you going to be updating this PR?

[kfcampbell]

Alright, I've spent a little more time looking into this. I can confirm the changes are as described:

• On main
  • With app_auth set, without token set, operation succeeds
  • With app_auth set, with token set, operation fails with the ConflictsWith error
• On branch
  • With app_auth set, without token set, operation succeeds
  • With app_auth set, with token set, operation succeeds

The PR that introduced app auth, #753, mentions that the app_auth block "conflicts deliberately" with the token, but doesn't specify why.

If this change unblocks others, I'm happy to ship it.

[MajorBreakfast]

@kfcampbell

Thanks!

This PR does not take into account your proposed alias keyword in #1537

alias is just Terraform's built-in way to distinguish between multiple instances of the same provider. It exists out-of-the-box on any provider.

[MajorBreakfast]

@kfcampbell any progress? Looking forward to next gh provider release with a fix :)

[MajorBreakfast]

@kfcampbell Is there an update? Looking forward to seeing this in a new version

[kfcampbell]

I'll get this merged now and released soon.