Proto 3.15 supports `optional` again!

[huan]

According to https://stackoverflow.com/a/62566052/1123955, we can get rid of the wrapper in our protos.

Presence tracking was added to proto3 in response to user feedback, both from inside Google and from open-source users. The proto3 wrapper types were previously the only supported presence mechanism for proto3. Users have pointed to both efficiency and usability issues with the wrapper types.

See: https://github.com/protocolbuffers/protobuf/blob/v3.12.0/docs/implementing_proto3_presence.md#background

This change will be a BREAKING CHANGE so it should be discussed later.

Useful Resources

• Google protobuf: if I add a field from one side will it break another one?
• Protobufs: Updating A Message Type

Blockers

• gen-grpc-gateway, gen-openapiv2: add support for proto3 optional
  • gen-grpc-gateway, gen-openapiv2: add support for proto3 optional grpc-ecosystem/grpc-gateway#1951
  • Released v2.3.0 (2021-02-25)
• Failed to generate pb file when using proto3 version.
  • Failed to generate pb file when using proto3 version. grpc/grpc-node#1717
  • grpc-tools v1.11.0: Bump protobuf dependency to 3.15.6 #1718
  • grpc-tools v1.11.1: make the plugin compatible with proto3 optional fields #1725
• grpc_tools_node_protoc_ts
  • Support 'optional' fields in proto3 agreatfool/grpc_tools_node_protoc_ts#88
• protoc-gen-lint
  • Support 'optional' fields in proto3 ckaznocha/protoc-gen-lint#20
• ts-protoc-gen (web gRPC)
  • Support for proto3 optional fields improbable-eng/ts-protoc-gen#263

More details

• How To Implement Field Presence for Proto3