emails: Update subject for confirm_new_email to have realm host.

Updates the email subject for confirming an email change to include
the realm host.

templates/zerver/emails/confirm_new_email.subject.txt

@@ -1 +1 @@
-{{ _("Verify your new email address") }}
+{% trans %}Verify your new email address for {{ organization_host }}{% endtrans %}

zerver/actions/user_settings.py

@@ -149,6 +149,7 @@ def do_start_email_change_process(user_profile: UserProfile, new_email: str) ->
         old_email=old_email,
         new_email=new_email,
         activate_url=activation_url,
+        organization_host=user_profile.realm.host,
     )
     language = user_profile.default_language
 

zerver/tests/test_email_change.py

@@ -39,7 +39,7 @@ class EmailChangeTestCase(ZulipTestCase):
         email_message = mail.outbox[0]
         self.assertEqual(
             email_message.subject,
-            "Verify your new email address",
+            "Verify your new email address for zulip.testserver",
         )
         body = email_message.body
         self.assertIn("We received a request to change the email", body)
@@ -168,7 +168,7 @@ class EmailChangeTestCase(ZulipTestCase):
         email_message = mail.outbox[0]
         self.assertEqual(
             email_message.subject,
-            "Verify your new email address",
+            "Verify your new email address for zulip.testserver",
         )
         body = email_message.body
         self.assertIn("We received a request to change the email", body)