Support new cloud block backend for Terraform Cloud

[GoodmanBen]

Resolves #75. Some other files were edited to fix small typos in documentation comments.

Adds a configuration attribute wherein the user specifies if the remote backend is_backend_terraform_cloud. This attribute defaults to false, so existing users not using the cloud block for their remote backend will not need to turn

Testing:

• Functionality works with a cloud bock specifying the backend with my use case. The tfmigrate block to handle this use case looks as follows:

tfmigrate {
  migration_dir = "."
  is_backend_terraform_cloud = true
  history {
    storage "local" {
      path = "./tfmigrate/history.json"
    }
  }
}

All tests pass when run folder by folder, except for some tests in TestExecutorEnv and TestExecutorDir which are failing when the tfexec folder's tests are run.

This might be an issue with how I'm trying to run the tests, since none of my changes should be effecting the presence of executables? If this is indeed a bug from my code changes, or if there is a better way to run the tests, please let me know! It is hard to see how the changes which pass in an integration test would lead to the observed testing error.

[minamijoyo]

@GoodmanBen Thank you for working on this and fixing many typos 😇

Your patch looks almost good. I left some review comments.

While some tests for executor depends on OS, it's no problem as long as the CI passes, but if you want to run it locally, run the test inside a docker-compose environment. The exact commands that CI is executing are as follows:

tfmigrate/.github/workflows/test.yaml

Lines 56 to 66 in 2959827

	- name: docker build
	run: docker-compose build
	- name: start localstack
	run: |
	docker-compose up -d localstack
	docker-compose run --rm dockerize -wait tcp://localstack:4566 -timeout 60s
	docker-compose exec -T localstack /docker-entrypoint-initaws.d/wait_s3_bucket_exists.sh
	- name: terraform --version
	run: docker-compose run --rm tfmigrate terraform --version
	- name: testacc
	run: docker-compose run --rm tfmigrate make testacc

As you pointed out in #77, it seems that we need a contribution guide. Sorry for your inconvenience.

[GoodmanBen]

@minamijoyo updated with the suggested changes and the linter fix. The NewMigrator interface is now unchanged and the IsBackendTerraformCloud boolean is passed down through the MigratorOption struct.

[minamijoyo]

LGTM 👍 Thank you for your contribution!

[minamijoyo]

@GoodmanBen Released it in v0.3.2 🚀