Add support for test environment variables

[aaabdelgany]

Description

This PR adds support for test environment variables to the tfe-provider. It does so in a separate tfe_test_variable as opposed to adding this to the tfe_variable resource. The tfe_variable resource currently supports workspace level variables and variable set level variables and parses HCL to determine which it's using. A new tfe_test specific variable was implemented to not contribute further to the complexity of the tfe_variable resource as well as to maintain the simplicity of the tfe_test_variable resource.
Remember to:

• Update the Change Log
• Update the Documentation

Testing plan

External links

Include any links here that might be helpful for people reviewing your PR. If there are none, feel free to delete this section.

• go-tfe documentation
• API documentation

Output from acceptance tests

Please run applicable acceptance tests locally and include the output here. See testing.md to learn how to run acceptance tests.

If you are an external contributor, your contribution(s) will first be reviewed before running them against the project's CI pipeline.

TF_ACC=1 TF_LOG_SDK_PROTO=OFF go test $(go list ./... |grep -v 'vendor') -v -run TestAccTFETestVariable -timeout 15m
?   	github.com/hashicorp/terraform-provider-tfe	[no test files]
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/terraform-provider-tfe/internal/client	0.164s [no tests to run]
testing: warning: no tests to run
PASS
ok  	github.com/hashicorp/terraform-provider-tfe/internal/logging	0.249s [no tests to run]
?   	github.com/hashicorp/terraform-provider-tfe/version	[no test files]
=== RUN   TestAccTFETestVariable_basic
--- PASS: TestAccTFETestVariable_basic (15.09s)
=== RUN   TestAccTFETestVariable_update
--- PASS: TestAccTFETestVariable_update (14.61s)
PASS
ok  	github.com/hashicorp/terraform-provider-tfe/internal/provider	30.198s
...

[brandonc]

Would you mind adding some docs for this resource to the website/docs/r directory? It would help our reviewing considerably. I also noticed a couple of things outright: is the resource importable? In the schema, organization is defined as optional but seems to be treated as required. See the other provider_next resources for proper org schema handling, because it may also come from the default defined in the provider config.

[aaabdelgany]

Would you mind adding some docs for this resource to the website/docs/r directory? It would help our reviewing considerably. I also noticed a couple of things outright: is the resource importable? In the schema, organization is defined as optional but seems to be treated as required. See the other provider_next resources for proper org schema handling, because it may also come from the default defined in the provider config.

The resource is not importable at this time - but that may change if a good use case for it arises. I've updated the required fields in the schema and added documentation. Please let me know if theres anything else I can do to facilitate the review process.

[ggambetti]

I'm not super familiar with provider code, and so the review is mostly questions. 😅

[ggambetti]

👍🏻