feat(storage): add feature tracking for async stub

[v-pratap]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a FeatureTracker utility to track and report client-side optimizations and configuration choices via the x-goog-storage-cpp-features header in both gRPC and REST clients. The reviewer recommends refactoring the duplicated logic for extracting and formatting the feature tracker header value into a shared helper function, FeatureTrackerHeaderValue, to comply with the repository's style guide against code duplication across three or more non-test files.

[gemini-code-assist]

To adhere to the repository style guide (which prefers to factor out duplicated code if it appears 3 or more times in non-test files), we should introduce a helper function FeatureTrackerHeaderValue to extract and format the feature tracker header value. This avoids repeating the same extraction logic in configure_client_context.h, stub.cc, and storage_stub_factory.cc.

// Evaluates client configuration options, creates a shared FeatureTracker
// initialized with configuration-driven feature flags (if any), and stores it
// into the Options list under FeatureTrackerOption.
Options SetupFeatureTracker(Options opts);

// Returns the feature tracker header value if feature reports are enabled and
// a tracker is present in the options, and the header value is not empty.
// Otherwise, returns an empty string.
std::string FeatureTrackerHeaderValue(Options const& options);

References

1. Prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)

[gemini-code-assist]

Implement the helper function FeatureTrackerHeaderValue to extract the feature tracker header value from options.

  return opts;
}

std::string FeatureTrackerHeaderValue(Options const& options) {
  if (options.has<EnableFeatureReportsOption>() &&
      !options.get<EnableFeatureReportsOption>()) {
    return {};
  }
  if (!options.has<FeatureTrackerOption>()) return {};
  auto const& tracker = options.get<FeatureTrackerOption>();
  if (!tracker) return {};
  return tracker->HeaderValue();
}

References

1. Prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)

[gemini-code-assist]

Use the helper function FeatureTrackerHeaderValue to avoid duplicating the feature tracker extraction logic, adhering to the repository style guide.

  auto const val = storage::internal::FeatureTrackerHeaderValue(options);
  if (!val.empty()) {
    ctx.AddMetadata(storage::internal::kFeatureTrackerHeaderName, val);
  }

References

1. Prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)

[gemini-code-assist]

Use the helper function FeatureTrackerHeaderValue to avoid duplicating the feature tracker extraction logic, adhering to the repository style guide.

  auto const val = FeatureTrackerHeaderValue(options);
  if (!val.empty()) {
    builder.AddHeader(kFeatureTrackerHeaderName, val);
  }

References

1. Prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)

[gemini-code-assist]

Use the helper function FeatureTrackerHeaderValue to avoid duplicating the feature tracker extraction logic, adhering to the repository style guide.

  auto const val = storage::internal::FeatureTrackerHeaderValue(options);
  if (!val.empty()) {
    fixed_metadata.emplace(storage::internal::kFeatureTrackerHeaderName, val);
  }

References

1. Prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)