Proposal for Support gRPC using Tonic

[davthecodercom]

Adding Support for gRPC #2946

Test

cd examples/grpc
cargo run

# Install grpcurl
brew install grpcurl

# Test unary call
grpcurl -plaintext -proto proto/greeter.proto -d '{"name": "World"}' localhost:50051 greeter.Greeter/SayHello
{
  "message": "Hello World! (from gRPC)"
}

# Test streaming call  
grpcurl -plaintext -proto proto/greeter.proto -d '{"name": "World"}' localhost:50051 greeter.Greeter/SayHelloStream
{
  "message": "Hello World (stream message 1)!"
}
{
  "message": "Hello World (stream message 2)!"
}
{
  "message": "Hello World (stream message 3)!"
}
{
  "message": "Hello World (stream message 4)!"
}
{
  "message": "Hello World (stream message 5)!"
}

Test HTTP endpoints:

curl http://localhost:8000/
curl http://localhost:8000/stats

Key Features

1. Dual Protocol Support: Serve both HTTP and gRPC from the same application
2. Shared State: Access Rocket's managed state from gRPC services
3. Streaming Support: Full support for unary and streaming gRPC methods
4. Easy Integration: Uses Rocket's fairing system for seamless integration
5. Tonic Integration: Built on top of the tonic gRPC library