An example of how a Flutter app interacts with Go services via gRPC

1. Moving code generation to a separate directory (repository) for gRPC

2. Sending a JWT token

3. Detailing the error in the response from the server via WithDetails

Various problems

1. grpc-web [WithDetails] : grpc/grpc-web#399

2. grpc-web [Client Streaming] : grpc/grpc-web#1205

3. grpc-web [CORS] : grpc/grpc-web#706