models: Add message type field.

zerver/migrations/0536_add_message_type.py

@@ -0,0 +1,26 @@
+# Generated by Django 5.0.6 on 2024-06-05 17:51
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("zerver", "0535_remove_realm_create_public_stream_policy"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="archivedmessage",
+            name="type",
+            field=models.PositiveSmallIntegerField(
+                choices=[(1, "Normal"), (2, "Resolve Topic Notification")], db_default=1, default=1
+            ),
+        ),
+        migrations.AddField(
+            model_name="message",
+            name="type",
+            field=models.PositiveSmallIntegerField(
+                choices=[(1, "Normal"), (2, "Resolve Topic Notification")], db_default=1, default=1
+            ),
+        ),
+    ]

zerver/models/messages.py

@@ -40,6 +40,27 @@ class AbstractMessage(models.Model):
     # Important for efficient indexes and sharding in multi-realm servers.
     realm = models.ForeignKey(Realm, on_delete=CASCADE)
 
+    class MessageType(models.IntegerChoices):
+        NORMAL = 1
+        RESOLVE_TOPIC_NOTIFICATION = 2
+
+    # IMPORTANT: message.type is not to be confused with the
+    # "recipient type" ("channel" or "direct"), which is is sometimes
+    # called message_type in the APIs, CountStats or some variable
+    # names. We intend to rename those to recipient_type.
+    #
+    # Type of the message, used to distinguish between "normal"
+    # messages and some special kind of messages, such as notification
+    # messages that may be sent by system bots.
+    type = models.PositiveSmallIntegerField(
+        choices=MessageType.choices,
+        default=MessageType.NORMAL,
+        # Note: db_default is a new feature in Django 5.0, so we don't use
+        # it across the codebase yet. It's useful here to simplify the
+        # associated database migration, so we're making use of it.
+        db_default=MessageType.NORMAL,
+    )
+
     # The message's topic.
     #
     # Early versions of Zulip called this concept a "subject", as in an email