The Are Multiple Sources of Truth for the gRPC interface

[zancas]

In particular the following files all define the CompactBlock type:

(1) ECC Rust Client LIbrary: zcash_client_backed

(2) ECC Go Zcashd Proxy: lightwalletd

(3) Zingolabs Rust Contract SDK: zingolib

Many sources of truth for the network interface eliminates one of the motivating benefits of a protobuf architecture, which is that the client and server are guaranteed to agree on an interface because they derive it from the same source!

Potential Solution:

• some repository contains the canonical specs (.protos) dependents reference those spec files. It seems obvious that the canonical spec files should be in lightwalletd.

[zancas]

Variants on the above solution:

• submodules of lightwalletd in e.g. zcash_client_backend
• commit-hash annotated (build.rs) scripts that use git to download the specs from a canonically located lightwalletd

[zancas]

Tracking this work here: https://github.com/zcash/librustzcash/issues/585