feat: Regenerate libraries with protobuf-4.x

[diegomarquezp]

This PR regenerates the client libraries using protobuf code generator 4.x

[gemini-code-assist]

Summary of Changes

Hello @diegomarquezp, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request undertakes a major regeneration of client libraries to incorporate protobuf-4.x, which is a foundational update impacting numerous API definitions and build processes. It also integrates new API surfaces for Google Actions SDK v2 and Google Ad Manager v1, significantly enhancing the project's scope. Concurrently, the PR refines the build and release pipeline through updated Bazel configurations, new scripts for Bazel Central Registry integration, and improved Cloud Build automation, ensuring a more robust and streamlined development workflow.

Highlights

• Protobuf Version Update: The client libraries have been regenerated to align with protobuf-4.x, ensuring compatibility with the latest Protocol Buffers features and improvements.
• Native Image Support for Spanner: Reflection configuration files for Google Cloud Spanner libraries have been updated to include new protobuf descriptor classes, enhancing native image compilation support.
• New API Definitions: This PR introduces comprehensive new API definitions for Google Actions SDK v2 and Google Ad Manager v1, expanding the available services and functionalities.
• Build and Release Infrastructure Overhaul: Significant updates to the project's build and release processes have been implemented, including new Bazel configurations, scripts for Bazel Central Registry (BCR) publishing, and Cloud Build automation.
• Documentation and Project Setup: New documentation files such as README.md, CONTRIBUTING.md, LICENSE, and SECURITY.md have been added or updated, alongside various configuration files for development and CI/CD.

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[gemini-code-assist]

Code Review

This pull request regenerates client libraries using protobuf 4.x and introduces a substantial amount of new tooling for Bazel, GitHub Actions, and publishing to the Bazel Central Registry. My review focused on the new scripts and configuration files. I've identified a few areas for improvement in the publish-to-bcr.sh script to enhance its robustness and clarity, such as handling file writes more safely and clarifying an outdated comment. I also noted a brittle dependency in the test script publish-to-bcr_test.sh that could be improved for long-term maintainability. Additionally, there's an unused --dry_run parameter that should be addressed.

[gemini-code-assist]

The use of > for in-place editing can be risky. If the jq command fails for any reason, ${metadata_file} might be truncated and left empty. A safer approach is to write the output to a temporary file first, and then replace the original file upon success.

Suggested change

	cat <<< $(jq ".versions += [\"${version}\"]" "${metadata_file}") > "${metadata_file}"
	jq ".versions += [\"${version}\"]" "${metadata_file}" > "${metadata_file}.tmp" && mv "${metadata_file}.tmp" "${metadata_file}"

[gemini-code-assist]

The --dry_run option is parsed but the dry_run variable is never used in the script. This could be misleading for users expecting a dry-run functionality. If this feature is intended for future use, it might be better to add a comment indicating it's not yet implemented or remove the option until it is. If it's a remnant of a removed feature, it should be deleted.

[gemini-code-assist]

The comment mentions master, but the command uses HEAD. It would be clearer to update the comment to reflect that HEAD is being used, which typically points to the default branch (e.g., main).

Suggested change

	echo "assuming templates_ref to be the HEAD of master"
	echo "assuming templates_ref to be the HEAD of the default branch"

[gemini-code-assist]

Sourcing functions from the main script using sed based on a comment is brittle. If the comment # parse input parameters is changed or removed in publish-to-bcr.sh, this test script will break. Consider refactoring the functions into a separate library file that can be sourced by both the main script and the test script for better maintainability.