Generates a Java client library from protocol buffers. Replaces the Java parts of the older monolithic generator.
See DEVELOPMENT.md for setting up development environment.
We use the src/main/proto/service_config.proto file to generate corresponding
Java class files.
They are needed to generate client libraries for gRPC-based Google services.
The source of src/main/proto/service_config.proto is the
https://github.com/grpc/grpc-proto repository.
We copy the file from the repository when a new enhancement is made in the file
and the service team asks us to incorporate the enhancement into the code
generator.