Add improved gRPC ecommerce example

[swistaczek]

Summary

• refine gRPC product page example
• use thread-safe caching with TTL
• document async fetch and caching

Testing

• bundle exec rake
• bundle exec rubocop example/grpc_ecommerce/product_page.rb

[Copilot]

Pull Request Overview

This pull request refines the gRPC product page example by introducing a thread‐safe caching mechanism with TTL, refining asynchronous data fetching with Concurrent::Promises, and updating documentation.

• Introduces a Liquid template for rendering product pages
• Implements concurrent data fetching with a thread-safe cache in product_page.rb
• Updates the README to document the new example

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
example/grpc_ecommerce/templates/product_page.liquid	Adds a new HTML template for the product page
example/grpc_ecommerce/product_page.rb	Implements async gRPC fetches and caching logic
example/grpc_ecommerce/README.md	Documents the updated gRPC ecommerce example

[Copilot]

Consider adding keyword_init: true to the ProductRequest struct definition to support the keyword argument usage in 'ProductRequest.new(id: id)'.

[Copilot]

Consider adding keyword_init: true to the RecommendationsRequest struct to allow keyword argument construction with 'RecommendationsRequest.new(product_id: id)'.