zulip_updates: Send zulip updates based on zulip_update_*_level.

This commit adds a management command that will run regularly
as a cron job to send zulip updates to realms based on their
current and latest zulip_update_announcements_level.

For realms with:
* level = None: Send a group DM to admins notifying them about
this new feature & suggestion to set the stream accordingly.

* level = 0:
  * If stream is still not configured, wait for a week
    before setting their level to latest level. They will
    miss updates until their configure the stream.
  * If stream is configured, send updates.

* level > 0: Send one message/update per level & increase
  the level by 1 till the latest level.

Fixes #28604.

zerver/tests/test_zulip_update_announcements.py

@@ -0,0 +1,154 @@
+from datetime import timedelta
+from unittest import mock
+
+import time_machine
+from django.conf import settings
+from django.utils.timezone import now as timezone_now
+
+from zerver.lib.test_classes import ZulipTestCase
+from zerver.lib.zulip_update_announcements import (
+    ZulipUpdateAnnouncement,
+    send_zulip_update_announcements,
+)
+from zerver.models.messages import Message
+from zerver.models.realms import get_realm
+from zerver.models.recipients import Recipient, get_huddle_user_ids
+from zerver.models.streams import get_stream
+from zerver.models.users import get_system_bot
+
+test_zulip_update_announcements = [
+    ZulipUpdateAnnouncement(
+        level=1,
+        message="Announcement message 1.",
+    ),
+    ZulipUpdateAnnouncement(
+        level=2,
+        message="Announcement message 2.",
+    ),
+]
+
+
+class ZulipUpdateAnnouncementsTest(ZulipTestCase):
+    @mock.patch(
+        "zerver.lib.zulip_update_announcements.zulip_update_announcements",
+        test_zulip_update_announcements,
+    )
+    def test_send_zulip_update_announcements(self) -> None:
+        realm = get_realm("zulip")
+
+        # realm predates the "zulip updates" feature with the
+        # zulip_update_announcements_stream set to None.
+        realm.zulip_update_announcements_level = None
+        realm.zulip_update_announcements_stream = None
+        realm.save(
+            update_fields=["zulip_update_announcements_level", "zulip_update_announcements_stream"]
+        )
+
+        group_direct_messages = Message.objects.filter(
+            realm=realm, recipient__type=Recipient.HUDDLE
+        )
+        self.assertFalse(group_direct_messages.exists())
+
+        admin_user_ids = set(realm.get_human_admin_users().values_list("id", flat=True))
+        notification_bot = get_system_bot(settings.NOTIFICATION_BOT, realm.id)
+        expected_group_direct_message_user_ids = admin_user_ids | {notification_bot.id}
+
+        now = timezone_now()
+        with time_machine.travel(now, tick=False):
+            send_zulip_update_announcements()
+
+        realm.refresh_from_db()
+        group_direct_message = group_direct_messages.first()
+        assert group_direct_message is not None
+        self.assertEqual(group_direct_message.sender, notification_bot)
+        self.assertEqual(group_direct_message.date_sent, now)
+        self.assertEqual(
+            set(get_huddle_user_ids(group_direct_message.recipient)),
+            expected_group_direct_message_user_ids,
+        )
+        self.assertEqual(realm.zulip_update_announcements_level, 0)
+        self.assertIn(
+            "These notifications are currently turned off in your organization.",
+            group_direct_message.content,
+        )
+
+        # Wait for one week before starting to skip sending updates.
+        with time_machine.travel(now + timedelta(days=2), tick=False):
+            send_zulip_update_announcements()
+        realm.refresh_from_db()
+        self.assertEqual(realm.zulip_update_announcements_level, 0)
+
+        with time_machine.travel(now + timedelta(days=8), tick=False):
+            send_zulip_update_announcements()
+        realm.refresh_from_db()
+        self.assertEqual(realm.zulip_update_announcements_level, 2)
+
+        # Configure a stream. Two new updates added.
+        verona = get_stream("verona", realm)
+        realm.zulip_update_announcements_stream = verona
+        realm.save(update_fields=["zulip_update_announcements_stream"])
+        new_updates = [
+            ZulipUpdateAnnouncement(
+                level=3,
+                message="Announcement message 3.",
+            ),
+            ZulipUpdateAnnouncement(
+                level=4,
+                message="Announcement message 4.",
+            ),
+        ]
+        test_zulip_update_announcements.extend(new_updates)
+
+        # verify zulip update announcements sent to configured stream.
+        with time_machine.travel(now + timedelta(days=10), tick=False):
+            send_zulip_update_announcements()
+        realm.refresh_from_db()
+        stream_messages = Message.objects.filter(
+            realm=realm,
+            sender=notification_bot,
+            recipient__type_id=verona.id,
+            date_sent__gte=now + timedelta(days=10),
+        ).order_by("id")
+        self.assert_length(stream_messages, 2)
+        self.assertEqual(stream_messages[0].content, "Announcement message 3.")
+        self.assertEqual(stream_messages[1].content, "Announcement message 4.")
+        self.assertEqual(realm.zulip_update_announcements_level, 4)
+
+    def test_group_direct_message_with_zulip_updates_stream_set(self) -> None:
+        realm = get_realm("zulip")
+
+        # realm predates the "zulip updates" feature.
+        realm.zulip_update_announcements_level = None
+        realm.save(update_fields=["zulip_update_announcements_level"])
+
+        self.assertIsNotNone(realm.zulip_update_announcements_stream)
+
+        group_direct_messages = Message.objects.filter(
+            realm=realm, recipient__type=Recipient.HUDDLE
+        )
+        self.assertFalse(group_direct_messages.exists())
+
+        admin_user_ids = set(realm.get_human_admin_users().values_list("id", flat=True))
+        notification_bot = get_system_bot(settings.NOTIFICATION_BOT, realm.id)
+        expected_group_direct_message_user_ids = admin_user_ids | {notification_bot.id}
+
+        now = timezone_now()
+        with time_machine.travel(now, tick=False):
+            send_zulip_update_announcements()
+
+        realm.refresh_from_db()
+        group_direct_message = group_direct_messages.first()
+        assert group_direct_message is not None
+        self.assertEqual(group_direct_message.sender, notification_bot)
+        self.assertEqual(group_direct_message.date_sent, now)
+        self.assertEqual(
+            set(get_huddle_user_ids(group_direct_message.recipient)),
+            expected_group_direct_message_user_ids,
+        )
+        self.assertEqual(realm.zulip_update_announcements_level, 0)
+        self.assertIn(
+            "Users in your organization will now receive "
+            "[updates](/help/configure-automated-notices#zulip-update-announcements) about new Zulip features in "
+            f"#**{realm.zulip_update_announcements_stream}>{realm.ZULIP_UPDATE_ANNOUNCEMENTS_TOPIC_NAME}**",
+            group_direct_message.content,
+        )