models: Add backward relation to MutedUser foreign keys.

Updates the two UserProfile foreign key fields to have a backward
relation in the MutedUser model by changing the `related_name`
property.

This is a prep commit for removing users with a muted relationship
to the current user from read receipts.

zerver/migrations/0411_alter_muteduser_muted_user_and_more.py

@@ -0,0 +1,33 @@
+# Generated by Django 4.0.7 on 2022-09-15 09:27
+
+import django.db.models.deletion
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("zerver", "0410_alter_stream_can_remove_subscribers_group"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="muteduser",
+            name="muted_user",
+            field=models.ForeignKey(
+                on_delete=django.db.models.deletion.CASCADE,
+                related_name="muted",
+                to=settings.AUTH_USER_MODEL,
+            ),
+        ),
+        migrations.AlterField(
+            model_name="muteduser",
+            name="user_profile",
+            field=models.ForeignKey(
+                on_delete=django.db.models.deletion.CASCADE,
+                related_name="muter",
+                to=settings.AUTH_USER_MODEL,
+            ),
+        ),
+    ]

zerver/models.py

@@ -2674,8 +2674,12 @@ class UserTopic(models.Model):
 
 
 class MutedUser(models.Model):
-    user_profile: UserProfile = models.ForeignKey(UserProfile, related_name="+", on_delete=CASCADE)
-    muted_user: UserProfile = models.ForeignKey(UserProfile, related_name="+", on_delete=CASCADE)
+    user_profile: UserProfile = models.ForeignKey(
+        UserProfile, related_name="muter", on_delete=CASCADE
+    )
+    muted_user: UserProfile = models.ForeignKey(
+        UserProfile, related_name="muted", on_delete=CASCADE
+    )
     date_muted: datetime.datetime = models.DateTimeField(default=timezone_now)
 
     class Meta: