Optimize protobuf specifications

[schancel]

User Story:
As a software architect, I want to ensure that the software is scalable and reliable. This means that requests should take the minimum amount of time to process and avoid deserializing and serializing data repeatedly.

Exit Criteria:
Protobuf spec is standardized in an acceptable way as to minimize wallet developer effort, and backend server computational load.

Impact:
Ensures service will be scalable in the future.