feat(generators): expose underlying OpenFeature client on generated clients

[kriscoleman]

Summary

• Exposes the underlying OpenFeature SDK client on all generated clients, allowing users to perform ad-hoc flag evaluations beyond what is defined in their manifest
• Each generator exposes the client in an idiomatic way for its language/framework:
  • Go: Exported Client package-level variable
  • Node.js: readonly client: Client property on GeneratedClient interface
  • Java: getOpenFeatureClient() method on GeneratedClient interface
  • C#: public IFeatureClient Client property on GeneratedClient
  • React: Re-exports useOpenFeatureClient hook from @openfeature/react-sdk
  • Angular: client getter on GeneratedFeatureFlagService returning the underlying FeatureFlagService
  • Python: Already publicly accessible via self.client (no change needed)
  • NestJS: Inherits client property from Node.js GeneratedClient (no change needed)

Test plan

• All existing golden file tests pass
• Go, Node.js, and C# integration tests updated to verify client accessibility
• Verify generated Go code compiles with generated.Client access
• Verify generated Node.js code works with client.client for ad-hoc evaluations
• Verify generated Java code compiles with getOpenFeatureClient() method
• Verify generated C# code compiles with Client property access
• Verify React re-export of useOpenFeatureClient works in a React app
• Verify Angular client getter works in an Angular app
• Verify Python self.client continues to work as expected
• Verify NestJS inherits client property correctly

[gemini-code-assist]

Code Review

This pull request updates the code generation templates for Angular, C#, Go, Java, Node.js, and React to expose the underlying OpenFeature client, enabling ad-hoc flag evaluations. Review feedback identifies potential naming collisions in the Go and Node.js generators where the generic name 'client' might conflict with user-defined flags. It is recommended to use more specific identifiers, such as 'OpenFeatureClient' or 'openFeatureClient', to avoid compilation errors and ensure the generated code remains robust regardless of the flag manifest content.

[kriscoleman]

let's drop last commit and keep with client, keep it a reserved word. We might be able to warn people if a flag matches. The real client should win out in a collision.

we discussed making it optional but the conditionals would get a bit messy