tests for protobuf stuff

[zramsay]

[liamsi]

Any specifics which tests we want to see? Sth. I would like to see is a check to circleci to check if the proto files were modified and the dev forgot to regenerate (if there is a diff in the proto files, regenerate code and see if there is a diff; this works better if we use a cargo.lock; ref: #70 )