Add warning documenting behavior of the google_service_account_key resource for certain cases where the project cannot be inferred by terraform

[stangles]

Resolves #9617.

[nat-henderson]

Hi - unfortunately this won't address the issue, since this repository is code-generated. Can you make the change to the upstream source of this information, in Magic Modules? https://github.com/GoogleCloudPlatform/magic-modules

[stangles]

Can you make the change to the upstream source of this information, in Magic Modules? https://github.com/GoogleCloudPlatform/magic-modules?

Yep! Thanks for the pointer, opened: GoogleCloudPlatform/magic-modules#5301

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.