[COMPLIANCE] Add copyright and license headers

[austinvalle]

Closes #259

This PR introduces:

• Add new tools module, add to dependabot, and move GRPC program to tools module dependencies
• make generate command that will auto-generate all copyright headers for this repo (hooks into go generate)
• make tools command to simplify the installation process of the Go specific tooling for make protoc target
  • Updated GH workflow to use this make tools command
• GH workflow that will error if copyright headers aren't present or if license is malformed
• Addition to the CONTRIBUTING.md on how to run license autogenerating commands

[austinvalle]

Along with the auto-generated files, I also ignored the .proto file, is that okay?

I believe comments would persist to the auto-generated file as well if we wanted to just ignore the auto-generated files only, i.e. *.pb.go and then I can run a make protoc

[bflad]

Hm the .proto files probably should have the copyright headers as they are intellectual property related. 👍 I thought the issue we saw elsewhere was that the comment would be injected into the middle of the .pb.go file instead of the top like copywrite wants, but maybe that's mistaken! grpc/grpc-go#5540 seems to suggest from the testing files that both protoc-gen-go and protoc-gen-go-grpc can put the comments at the top, maybe?

[austinvalle]

Cool! I added an ignore just for the .pb.go files and then ran a make protoc:

 $ make generate
cd tools; go generate ./...
Using license identifier: MPL-2.0
Using copyright holder: HashiCorp, Inc.

Exempting the following search patterns:
.changes/unreleased/*.yaml
.changie.yaml
.github/ISSUE_TEMPLATE/*.yml
.github/labeler-*.yml
.golangci.yml
.goreleaser.yml
.release/*.hcl
tfprotov5/internal/tfplugin5/*.pb.go
tfprotov6/internal/tfplugin6/*.pb.go

The following files are missing headers:
2023-06-05T12:31:48.015-0400 [INFO]  cli: tfprotov5/internal/tfplugin5/tfplugin5.proto modified
2023-06-05T12:31:48.016-0400 [INFO]  cli: tfprotov6/internal/tfplugin6/tfplugin6.proto modified

[bflad]

Looks good to me 🚀

[bflad]

Looks good to me 🚀

[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 contributions.
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.