Move POST /v1/insights/:id/dismiss to /v1/insights/:id/dismissals
and POST /v1/insights/:id/ctas/:ctaId/trigger to
/v1/insights/:id/ctas/:ctaId/executions, with the corresponding
class moves into Http/Insights/Dismissal/Create.php and
Http/CTA/Execution/Create.php. Rename the response model to
InsightCtaExecution and update events.php to surface dismissal
and execution as resource events with create verbs. The reshape
matches the rest of the API where verbs hang off plural sub-resources.