Correct the extension used for Roundcube overrides

This adds ".inc.php" files to the included overrides while maintaining
support for existing ".inc" files previously included via overrides.

Roundcube itself uses "inc.php" files and these overrides are expected
to match that format. Switching to "inc.php" both tells the user that
these need to be proper php files and conveys they are used for changing
the same settings that Roundcube's inc.php files modify.

docs/faq.rst

@@ -267,7 +267,7 @@ correct syntax. The following file names will be taken as override configuration
 - `Dovecot`_ - ``dovecot.conf`` in dovecot sub-directory;
 - `Nginx`_ - All ``*.conf`` files in the ``nginx`` sub-directory;
 - `Rspamd`_ - All files in the ``rspamd`` sub-directory.
-- Roundcube - All ``*.inc`` files in the ``roundcube`` sub directory.
+- `Roundcube`_ - All ``*.inc.php`` files in the ``roundcube`` sub directory.
 
 To override the root location (``/``) in Nginx ``WEBROOT_REDIRECT`` needs to be set to ``none`` in the env file (see :ref:`web settings <web_settings>`).
 
@@ -354,10 +354,11 @@ How do I use webdav (radicale)?
 *issue reference:* `1591`_.
 
 
-.. _`Postfix`: http://www.postfix.org/postconf.5.html
-.. _`Dovecot`: https://doc.dovecot.org/configuration_manual/config_file/config_file_syntax/
-.. _`NGINX`:   https://nginx.org/en/docs/
-.. _`Rspamd`:  https://www.rspamd.com/doc/configuration/index.html
+.. _`Postfix`:   http://www.postfix.org/postconf.5.html
+.. _`Dovecot`:   https://doc.dovecot.org/configuration_manual/config_file/config_file_syntax/
+.. _`NGINX`:     https://nginx.org/en/docs/
+.. _`Rspamd`:    https://www.rspamd.com/doc/configuration/index.html
+.. _`Roundcube`: https://github.com/roundcube/roundcubemail/wiki/Configuration#customize-the-look
 
 .. _`Docker swarm howto`: https://github.com/Mailu/Mailu/tree/master/docs/swarm/master
 .. _`125`: https://github.com/Mailu/Mailu/issues/125

towncrier/newsfragments/2388.bugfix

@@ -0,0 +1 @@
+Roundcube overrides now also include .inc.php files. Only .inc.php should be used moving forward.

webmails/roundcube/start.py

@@ -60,7 +60,7 @@ else:
 context["PLUGINS"] = ",".join(f"'{p}'" for p in plugins)
 
 # add overrides
-context["INCLUDES"] = sorted(inc for inc in os.listdir("/overrides") if inc.endswith(".inc")) if os.path.isdir("/overrides") else []
+context["INCLUDES"] = sorted(inc for inc in os.listdir("/overrides") if inc.endswith((".inc", ".inc.php"))) if os.path.isdir("/overrides") else []
 
 # calculate variables for config file
 context["SESSION_TIMEOUT_MINUTES"] = max(int(env.get("SESSION_TIMEOUT", "3600")) // 60, 1)