15180 Explain task use for posModel creation

Author: joshheald

WooCommerce/Classes/POS/Presentation/PointOfSaleEntryPointView.swift

@@ -35,6 +35,9 @@ struct PointOfSaleEntryPointView: View {
             }
         }
         .task {
+            // We create the posModel in a task, not init, to avoid creating multiple copies during the view's lifecycle.
+            // Confusingly, init can be called more than once, but `task` matches the lifecycle.
+            // See https://developer.apple.com/documentation/swiftui/state#Store-observable-objects for details.
             posModel = PointOfSaleAggregateModel(
                 itemsController: itemsController,
                 cardPresentPaymentService: cardPresentPaymentService,