Publish Schedule schema

[lacarvalho91]

Currently users just copy the Schedule case class into their projects, which is far from ideal.

Couple of potential options:

• run a schema registry somewhere for the KMS (no idea where that would be!)
• publish the Schedule case class in a JAR and release it
• both?

Another thing we should do is validate changes to the Schedule schema during PRs, this would need to call a schema registry somewhere using the compatibility API