Protobuf Schema Versioning

[nking-1]

Is your feature request related to a problem? Please describe. When we have host a guidance-enabled API that marshals data through protobuf, we'll need to add or modify the existing fields over the lifetime of the service. We will need to have a version field in the protobuf spec in order to determine data compatibility as the service is updated.

Describe the solution you'd like Add a version somewhere in the spec, for example:

message Grammar {
    repeated GrammarFunction nodes = 1;
    int32 version = 2;
}

Add tests to verify that there's a version parameter specified in a message.

Additional info We've chatted among the team inside Microsoft and hope to have this done before deploying a public service.