[VI-1056] updates factory & adds attribute validations

[bramleyjl]

Summary

• Updates UserActionEvent class to validate event_id & event_type as not null

Related issue(s)

• https://jira.devops.va.gov/browse/VI-1056

Testing done

• New code is covered by unit tests
• manually create UserActionEvent instances to test the attribute validations

 => UserActionEvent(id: integer, details: string, created_at: datetime, updated_at: datetime, event_id: string, event_type: integer) 
3.3.6 :002 > UserActionEvent.new(details: 'test details', event_id: 'some-event-id', event_type: 2).valid?
 => true 
3.3.6 :003 > UserActionEvent.new(details: 'test details', event_id: 'some-event-id', event_type: nil).valid?
 => false 
3.3.6 :004 > UserActionEvent.new(details: 'test details', event_type: 2).valid?
 => false