Allow Scala-like Message Definitions

[reid-spencer]

Is your feature already requested in another issue?

No.

Is your feature a defect?

No.

Is your feature request related to a problem? Please describe.

A more compact form of message definition needs be provided.

Describe the solution you'd like

Use the syntax of a Scala case class to define a record, command, event, query or result. For example:

command DoIt(at: Location, what: String, when: Timestamp)

Describe the alternatives you've considered

None considered.

Additional Context

None