Add snapshot/api diff checks to verify serialization

[zastrowm]

We should have serialization tests or another enforcement mechanism to ensure that messages serialized in a previous version of the SDK continues to work in the newest versions; e.g. renames don't break consumers

Gotcha, makes sense. We should probably add an api diff check or something too because if we break these interfaces, then serialization breaks

Originally posted by @Unshure in #548 (comment)