apache: Enable expires module by default

- Can be used to set the 'Expires:' header to cache static files for a long
time.

Tests:

- Without the patch 'a2query -m expires' shows that the module is not installed.
Applying the patches and restarting services shows that Apache app's setup is
run and 'a2query -m expires' shows that module is enabled.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/modules/apache/__init__.py

@@ -22,7 +22,7 @@ class ApacheApp(app_module.App):
 
     app_id = 'apache'
 
-    _version = 13
+    _version = 14
 
     def __init__(self) -> None:
         """Create components for the app."""

plinth/modules/apache/privileged.py

@@ -88,6 +88,7 @@ def setup(old_version: int):
         webserver.enable('proxy_html', kind='module')
         webserver.enable('rewrite', kind='module')
         webserver.enable('macro', kind='module')
+        webserver.enable('expires', kind='module')
 
         # Disable logging into files, use FreedomBox configured systemd logging
         webserver.disable('other-vhosts-access-log', kind='config')