notif: Create summary notification

Reimplement the summary notification implementation
from zulip-mobile:
  https://github.com/zulip/zulip-mobile/blob/6d5d56d175644cd0cdf47f3cd30ffadf6756bbdc/android/app/src/main/java/com/zulipmobile/notifications/NotificationUiManager.kt#L299-L382

Fixes: #569
Fixes: #571

Author: rajveermalviya

lib/notifications/display.dart

@@ -89,7 +89,7 @@ class NotificationDisplayManager {
     }
   }
 
-  static void _onMessageFcmMessage(MessageFcmMessage data, Map<String, dynamic> dataJson) {
+  static Future<void> _onMessageFcmMessage(MessageFcmMessage data, Map<String, dynamic> dataJson) async {
     assert(debugLog('notif message content: ${data.content}'));
     final zulipLocalizations = GlobalLocalizations.zulipLocalizations;
     final title = switch (data.recipient) {
@@ -103,13 +103,16 @@ class NotificationDisplayManager {
       FcmMessageDmRecipient() =>
         data.senderFullName,
     };
-    final conversationKey = _conversationKey(data);
-    ZulipBinding.instance.androidNotificationHost.notify(
+    final groupKey = _groupKey(data);
+    final conversationKey = _conversationKey(data, groupKey);
+
+    await ZulipBinding.instance.androidNotificationHost.notify(
       // TODO the notification ID can be constant, instead of matching requestCode
       //   (This is a legacy of `flutter_local_notifications`.)
       id: notificationIdAsHashOf(conversationKey),
       tag: conversationKey,
       channelId: NotificationChannelManager.kChannelId,
+      groupKey: groupKey,
 
       contentTitle: title,
       contentText: data.content,
@@ -139,6 +142,22 @@ class NotificationDisplayManager {
         // TODO this doesn't set the Intent flags we set in zulip-mobile; is that OK?
         //   (This is a legacy of `flutter_local_notifications`.)
         ),
+      autoCancel: true,
+    );
+
+    await ZulipBinding.instance.androidNotificationHost.notify(
+      id: notificationIdAsHashOf(groupKey),
+      channelId: NotificationChannelManager.kChannelId,
+      tag: groupKey,
+      groupKey: groupKey,
+      isGroupSummary: true,
+      color: kZulipBrandColor.value,
+      // TODO vary notification icon for debug
+      smallIconResourceName: 'zulip_notification', // This name must appear in keep.xml too: https://github.com/zulip/zulip-flutter/issues/528
+      inboxStyle: InboxStyle(
+        // TODO(#570) Show organization name, not URL
+        summaryText: data.realmUri.toString()),
+      autoCancel: true,
     );
   }
 
@@ -157,8 +176,7 @@ class NotificationDisplayManager {
       | ((bytes[3] & 0x7f) << 24);
   }
 
-  static String _conversationKey(MessageFcmMessage data) {
-    final groupKey = _groupKey(data);
+  static String _conversationKey(MessageFcmMessage data, String groupKey) {
     final conversation = switch (data.recipient) {
       FcmMessageStreamRecipient(:var streamId, :var topic) => 'stream:$streamId:$topic',
       FcmMessageDmRecipient(:var allRecipientIds) => 'dm:${allRecipientIds.join(',')}',

test/notifications/display_test.dart

@@ -111,11 +111,13 @@ void main() {
       required String expectedTagComponent,
     }) {
       final expectedTag = '${data.realmUri}|${data.userId}|$expectedTagComponent';
+      final expectedGroupKey = '${data.realmUri}|${data.userId}';
       final expectedId =
         NotificationDisplayManager.notificationIdAsHashOf(expectedTag);
       const expectedIntentFlags =
         PendingIntentFlag.immutable | PendingIntentFlag.updateCurrent;
-      check(testBinding.androidNotificationHost.takeNotifyCalls()).single
+      final calls = testBinding.androidNotificationHost.takeNotifyCalls();
+      check(calls[0])
         ..id.equals(expectedId)
         ..tag.equals(expectedTag)
         ..channelId.equals(NotificationChannelManager.kChannelId)
@@ -124,11 +126,31 @@ void main() {
         ..color.equals(kZulipBrandColor.value)
         ..smallIconResourceName.equals('zulip_notification')
         ..extras.isNull()
+        ..groupKey.equals(expectedGroupKey)
+        ..isGroupSummary.isNull()
+        ..inboxStyle.isNull()
+        ..autoCancel.equals(true)
         ..contentIntent.which((it) => it.isNotNull()
           ..requestCode.equals(expectedId)
           ..flags.equals(expectedIntentFlags)
           ..intentPayload.equals(jsonEncode(data.toJson()))
         );
+      check(calls[1])
+        ..id.equals(NotificationDisplayManager.notificationIdAsHashOf(expectedGroupKey))
+        ..tag.equals(expectedGroupKey)
+        ..channelId.equals(NotificationChannelManager.kChannelId)
+        ..contentTitle.isNull()
+        ..contentText.isNull()
+        ..color.equals(kZulipBrandColor.value)
+        ..smallIconResourceName.equals('zulip_notification')
+        ..extras.isNull()
+        ..groupKey.equals(expectedGroupKey)
+        ..isGroupSummary.equals(true)
+        ..inboxStyle.which((it) => it.isNotNull()
+          ..summaryText.equals(data.realmUri.toString())
+        )
+        ..autoCancel.equals(true)
+        ..contentIntent.isNull();
     }
 
     Future<void> checkNotifications(FakeAsync async, MessageFcmMessage data, {