models: Add field is_announcement_only to stream.

zerver/migrations/0169_stream_is_announcement_only.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.6 on 2018-05-12 04:57
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('zerver', '0168_stream_is_web_public'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='stream',
+            name='is_announcement_only',
+            field=models.BooleanField(default=False),
+        ),
+    ]

zerver/models.py

@@ -962,6 +962,7 @@ class Stream(models.Model):
 
     date_created = models.DateTimeField(default=timezone_now)  # type: datetime.datetime
     deactivated = models.BooleanField(default=False)  # type: bool
+    is_announcement_only = models.BooleanField(default=False)  # type: bool
 
     def __str__(self) -> str:
         return "<Stream: %s>" % (self.name,)