shouldHandleForEngagement
Extension function to check if a SilentPushEvent should be handled for ENGAGEMENT destination.
Parses the context field (_co) from pushData to extract destination information. Silent pushes should be processed if they are destined for ENGAGEMENT or have UNKNOWN destination. If the context field is missing or null, defaults to UNKNOWN (which passes the filter).
Return
true if the event should be handled for ENGAGEMENT, false otherwise