The descriptions for "Model Ready" and "Model Metadata" in both the REST and gRPC specifications claim that the model version is optional. Is this true? If so, the specification should report it's optionality in more than a comment/description (optional in proto3 and required: false in openAPI). If the version is optional in the REST protocol, should there instead be another versionless route instead of eg, '/v2/models/${MODEL_NAME}/versions/${MODEL_VERSION}/ready'?