settings: Include units in SERVER_UPGRADE_NAG_DEADLINE_DAYS name.

When naming things with units of time involved, it's always good to
include units in the name, so that the meaning is clear.

zerver/lib/home.py

@@ -61,7 +61,9 @@ def is_outdated_server(user_profile: Optional[UserProfile]) -> bool:
     ).replace(tzinfo=pytz.utc)
 
     version_no_newer_than = min(LAST_SERVER_UPGRADE_TIME, release_build_time)
-    deadline = version_no_newer_than + datetime.timedelta(days=settings.SERVER_UPGRADE_NAG_DEADLINE)
+    deadline = version_no_newer_than + datetime.timedelta(
+        days=settings.SERVER_UPGRADE_NAG_DEADLINE_DAYS
+    )
 
     if user_profile is None or not user_profile.is_realm_admin:
         # Administrators get warned at the deadline; all users 30 days later.

zerver/tests/test_home.py

@@ -876,7 +876,7 @@ class HomeTest(ZulipTestCase):
             compute_navbar_logo_url(page_params), "/static/images/logo/zulip-org-logo.svg?version=0"
         )
 
-    @override_settings(SERVER_UPGRADE_NAG_DEADLINE=365)
+    @override_settings(SERVER_UPGRADE_NAG_DEADLINE_DAYS=365)
     def test_is_outdated_server(self) -> None:
         # Check when server_upgrade_nag_deadline > last_server_upgrade_time
         hamlet = self.example_user("hamlet")

zproject/default_settings.py

@@ -446,4 +446,4 @@ DEFAULT_DATA_EXPORT_IMPORT_PARALLELISM = (len(os.sched_getaffinity(0)) // 2) or
 # to be upgraded because of likely security releases in the meantime.
 # Default is 18 months, constructed as 12 months before someone should
 # upgrade, plus 6 months for the system administrator to get around to it.
-SERVER_UPGRADE_NAG_DEADLINE = 30 * 18
+SERVER_UPGRADE_NAG_DEADLINE_DAYS = 30 * 18