wip push_device add thisDevice getter

Author: gnprice

lib/model/push_device.dart

@@ -46,10 +46,18 @@ class PushDeviceManager extends PerAccountStoreBase {
   ///
   /// An absent map in [InitialSnapshot] (from an old server) is treated
   /// as empty, since a server without this feature has none of these records.
+  ///
+  /// See also [thisDevice].
   // TODO(server-11) simplify doc re an absent map
   late Map<int, PushDeviceEntry> pushDevices = UnmodifiableMapView(_pushDevices);
   final Map<int, PushDeviceEntry> _pushDevices;
 
+  /// The push-device registration status the server currently reports for
+  /// this very install of the app, if any.
+  ///
+  /// This is an entry in [pushDevices].
+  PushDeviceEntry? get thisDevice => _pushDevices[account.pushAccountId];
+
   void handlePushDeviceEvent(PushDeviceEvent event) {
     final pushAccountId = int.tryParse(event.pushAccountId, radix: 10);
     if (pushAccountId == null) return; // TODO(log); TODO(#1764) push this to API parser