feat: update tracing hook to latest semantic conventions

[Vadman97]

Summary

Updates the Ruby OpenTelemetry tracing hook to comply with the latest OpenTelemetry semantic conventions specification for feature flag instrumentation. This brings the Ruby SDK in line with other LaunchDarkly SDKs (Java, Go, .NET).

Link to Devin run: https://app.devin.ai/sessions/00115de67e494cc999f5c247414cd9b1
Requested by: @Vadman97

Changes

Attribute Name Updates (Breaking for Observability Consumers)

• feature_flag.context.key → feature_flag.context.id
• feature_flag.provider_name → feature_flag.provider.name
• feature_flag.variant → feature_flag.result.value

New Configuration Options

• include_value: Replaces deprecated include_variant option. Controls whether flag values are included in telemetry.
• environment_id: Optional string parameter that adds feature_flag.set.id attribute. Validates non-empty strings and logs warnings for invalid input.

New Optional Attributes

• feature_flag.result.reason.inExperiment: Set to true when evaluation is part of an experiment
• feature_flag.result.variationIndex: Includes variation index when available

Backward Compatibility

• include_variant option continues to work via fallback logic: opts.fetch(:include_value, opts.fetch(:include_variant, false))
• Added test coverage for deprecated option to ensure backward compatibility

Bug Fixes

• Fixed initialization order bug where validate_environment_id was called before @logger was initialized, causing NoMethodError on Ruby 3.0/3.1

Testing

• All existing tests updated to use new attribute names
• New test contexts added for:
  • include_value configuration
  • include_variant backward compatibility
  • environment_id configuration (valid and invalid cases)
  • inExperiment and variationIndex attributes
• All CI checks passing on Ruby 3.0, 3.1, 3.2, jruby-9.4, and Windows

Review Checklist

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

⚠️ Critical Review Items

1. Test logic for inExperiment (line 221 in spec): The test "includes inExperiment when evaluation is part of experiment" verifies the attribute is NOT present (.to be false). Please verify this is correct behavior - is the test setup actually creating an experiment scenario, or is this testing the default case?

2. Backward compatibility: Verify the nested fallback pattern opts.fetch(:include_value, opts.fetch(:include_variant, false)) works correctly for all combinations of options.

3. Initialization order: The constructor now sets @logger before calling validate_environment_id. Verify this doesn't break any assumptions about initialization sequence.

4. Environment validation: The environment_id validation only checks for non-empty strings. Confirm this matches the spec requirements (no format/character restrictions needed?).

Related Issues

• Specification: https://raw.githubusercontent.com/launchdarkly/sdk-specs/refs/heads/main/specs/OTEL-openteletry-integration/README.md
• Reference implementations:
  • Java SDK: feat: Update OpenTelemetry semantic conventions java-core#89
  • .NET SDK: feat: Updating semantic conventions dotnet-core#148
  • Go SDK: feat: Support latest feature flagging semantic conventions. go-server-sdk#292

Additional Context

• Unable to run Rubocop locally due to missing Ruby development headers in environment. All lint verification was done via CI.
• Changes are focused on the ruby-server-sdk-otel package; the main ruby-server-sdk package does not require updates.

[devin-ai-integration]

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[devin-ai-integration]

Thanks for the code review @keelerm84! I've applied both style suggestions:

1. ✅ Changed to inline private modifier: private def validate_environment_id(env_id)
2. ✅ Refactored to guarded return style for better readability

All CI checks are passing with these changes.