Further reading
- The official Protobuf language guide:
https://developers.google.com/protocol-buffers/docs/proto3
- Specifying custom options in Protobuf:
https://developers.google.com/protocol-buffers/docs/proto#extensions
https://developers.google.com/protocol-buffers/docs/proto3
https://developers.google.com/protocol-buffers/docs/proto#extensions