Event priming and assertion tooling

[purple52]

We need new utility classes to simplify the process of working with events in tests.

Event Priming

• Allow tests to prime an event store with some events in a way that stores them and (optionally) publishes them
• Events might be provided via Java code, or via JSON files
• Events might need to be primed in multiple data sources
• Event metadata that is normally set by the event store might need to be specified explicitly
• Option needed to assert against a view store to confirm that all the events have been consumed, probably by polling the stream status table

Event Assertions

• Allow tests to do assertions against the event store to confirm that a stream is in a certain state
• Expected events might be provided via Java code, or via JSON files
• Assertions might need to ignore some metadata when comparing
• Assertions might need to wait and/or check that no additional events are stored.