feat(workloadidentity): generate library

[scotthart]

PiperOrigin-RevId: 962846928

[gemini-code-assist]

Code Review

This pull request introduces the new Workload Identity API C++ client library, including its generated implementation, build configurations, documentation, and a quickstart sample. The review feedback highlights a critical issue in the quickstart's WORKSPACE.bazel file, which incorrectly fetches v3.8.0 of google-cloud-cpp instead of v3.9.0, leading to build failures. Additionally, it is recommended to use conditional assignment (?=) in the quickstart's Makefile to allow users to override compiler and flag variables.

[gemini-code-assist]

The quickstart WORKSPACE.bazel currently fetches v3.8.0 of google-cloud-cpp. However, workloadidentity is a new library being introduced in v3.9.0 (as per the changelog). Consequently, building this quickstart using this WORKSPACE.bazel will fail because the workloadidentity target does not exist in v3.8.0. Please ensure that when updating the version of google-cloud-cpp in the http_archive rule, the sha256 hash is also updated to match the new version's content.

References

1. When updating the version of a dependency in an http_archive rule in a Bazel WORKSPACE file, the sha256 hash must also be updated to match the new version's content.

[gemini-code-assist]

Hardcoding CXX, CXXFLAGS, and CXXLD prevents users from easily overriding the compiler and flags (e.g., to clang++ on macOS). Using ?= allows these variables to be overridden from the environment or command line.

CXX?=g++
CXXFLAGS?=-std=c++17
CXXLD?=$(CXX)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.24%. Comparing base (b6ddf66) to head (48759fe).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16349   +/-   ##
=======================================
  Coverage   92.23%   92.24%           
=======================================
  Files        2227     2227           
  Lines      209543   209543           
=======================================
+ Hits       193282   193288    +6     
+ Misses      16261    16255    -6     

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