Implement unified multi-language gRPC code generator

[Copilot]

This PR implements a comprehensive build tool that generates gRPC server and client code for multiple programming languages from a centralized set of Protocol Buffer definitions.

Problem Statement

Previously, the repository contained separate gRPC examples scattered across different directories, each with its own proto files and build scripts. This made it difficult to maintain consistency and required manual synchronization when making API changes.

Solution

Implemented a unified build tool (codegen.js) that:

• Centralizes proto definitions in a single proto/ directory
• Generates code for 4 languages: Go, Python, TypeScript/NestJS, and Rust
• Provides a single command interface via npm scripts
• Automatically manages dependencies and tool installation
• Creates organized output structure with language-specific optimizations

Key Features

Multi-Language Support

• Go: Uses protoc-gen-go and protoc-gen-go-grpc for modern gRPC generation
• Python: Uses grpcio-tools with complete type hint support (.pyi files)
• TypeScript: Uses ts-proto with both general TypeScript and NestJS-specific variants
• Rust: Uses tonic-build for async gRPC with complete Cargo project structure

Developer Experience

# Generate for all languages
npm run build

# Generate for specific language
npm run build:go
npm run build:python  
npm run build:typescript
npm run build:rust

Automatic Setup

• Cross-platform protoc compiler auto-installation (Linux, macOS, Windows)
• Language-specific plugin installation (Go tools, Python grpcio-tools, etc.)
• Dependency management with proper error handling

Generated Structure

generated/
├── go/                     # Go .pb.go and _grpc.pb.go files
├── python/                 # Python .py, .pyi, and _grpc.py files
├── typescript/             # TypeScript interfaces
│   └── nestjs/            # NestJS decorators and metadata
└── rust/                  # Complete tonic-based Rust project

Documentation

Added comprehensive documentation:

• BUILD.md - Build tool usage and configuration
• EXAMPLES.md - Complete usage examples for all languages
• SOLUTION.md - Technical implementation details
• Updated README.md with new workflow

Testing

Verified that the tool:

• ✅ Generates syntactically correct code for all languages
• ✅ Handles missing dependencies gracefully with auto-installation
• ✅ Works across different platforms
• ✅ Provides clear error messages and progress feedback
• ✅ Maintains backward compatibility with existing examples

This implementation transforms the repository from a collection of separate examples into a production-ready, unified gRPC development toolkit that significantly improves developer productivity and maintains consistency across multiple programming languages.

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