Lack of gRPC client integration tests

[blewater]

The Cosmos Stargate SDK upgrade introduced Protobuf serialization and gRPC as the API interface. Even the revamped Rest endpoints are served through the gRPC gateway pipe and lose their simplicity benefits when signing transactions. 
While the code base features Gingko integration tests, these exercise the CLI interface hardly the nominal choice for integrating external applications.

Exceptions

1. A POC demonstrating legacy transaction signing compatibility with the Ledger device through the CosmJS library.

2. A gRPC client with minimal API surface for query/response and transaction signing layer for the Bep3 module.

Proposed Solutions

• Replace a good portion of the existing Gingko tests with the CosmJS library that uses Protobuf and gRPC in its Stargate edition the defacto standard for external application integration work. Moreover, the same tests would function as an on-boarding aid and functional code samples for front-end integration work.

• Test with an enhanced gRPC Client. An obvious benefit is a tight integration with the existing Go source base and rapid implementation speed. They may also form the basis for a future em-ledger SDK for Golang integrators, though unlikely a popular choice for the envisioned audiences.