walks: use dateUtils instead of new Date and prefer future events, reuse contact components on event detail (#200)
When multiple events match a URL slug, prefer exact URL slug matches,
future events over past, and most recent as tiebreaker
Rename WalkLeaderComponent to EventLeaderComponent and WalkGroupComponent
to EventGroupComponent to reflect that the data model is ExtendedGroupEvent
with different item types (group-walk, group-event)
Reuse EventLeaderComponent on group-event detail view for DRY contact
handling (contact-us routing, WhatsApp/SMS dropdown, copy icons)
Remove duplicated contact details markup from group-event-view