feat: serve a subscribable ICS calendar feed

controllers/api/api.go

@@ -33,6 +33,10 @@ type Handlers struct {
 	PerPage int
 	// DashboardLimit is the number of sessions and deadlines on /dashboard.
 	DashboardLimit int
+	// PublicURL is the absolute base URL of the application
+	// (jz.bm.public_url), used for the calendar feed URL and the links in
+	// it. Empty means the scheme and Host of the request.
+	PublicURL string
 }
 
 func (h *Handlers) now() time.Time {