Introduced redis session handler does not work with non-root images

In commit 83ea69d54bea72e1df9a2647ee101c73deb86d44, a redis session handler was intrododuced. But the file /usr/local/etc/php/conf.d/redis-session.ini can not be written when using a non-root image, because the folder is owned by root and the default www-data user does not have write permission.

/var/www/html # ls -lha /usr/local/etc/php/conf.d
total 72
drwxr-xr-x    1 root     root        4.0K Feb 26 08:50 .
drwxr-xr-x    1 root     root        4.0K Feb 26 07:34 ..
-rw-r--r--    1 root     root          35 Feb 26 08:50 docker-php-ext-apcu.ini
-rw-r--r--    1 root     root          18 Feb 26 08:47 docker-php-ext-exif.ini
-rw-r--r--    1 root     root          16 Feb 26 08:47 docker-php-ext-gd.ini
-rw-r--r--    1 root     root          21 Feb 26 08:50 docker-php-ext-imagick.ini
-rw-r--r--    1 root     root          18 Feb 26 08:48 docker-php-ext-intl.ini
-rw-r--r--    1 root     root          18 Feb 26 08:48 docker-php-ext-ldap.ini
-rw-r--r--    1 root     root          23 Feb 26 08:50 docker-php-ext-memcached.ini
-rw-r--r--    1 root     root          82 Feb 26 08:48 docker-php-ext-opcache.ini
-rw-r--r--    1 root     root          19 Feb 26 08:48 docker-php-ext-pcntl.ini
-rw-r--r--    1 root     root          23 Feb 26 08:49 docker-php-ext-pdo_mysql.ini
-rw-r--r--    1 root     root          23 Feb 26 08:49 docker-php-ext-pdo_pgsql.ini
-rw-r--r--    1 root     root          19 Feb 26 08:50 docker-php-ext-redis.ini
-rw-r--r--    1 root     root          20 Feb 26 07:34 docker-php-ext-sodium.ini
-rw-r--r--    1 root     root          17 Feb 26 08:49 docker-php-ext-zip.ini
-rw-r--r--    1 root     root          18 Feb 26 08:50 memory-limit.ini
-rw-r--r--    1 root     root         189 Feb 26 08:50 opcache-recommended.ini

For running my nextcloud image, I use the default non-privileged user www-data.

/var/www/html $ id
uid=82(www-data) gid=82(www-data) groups=82(www-data)

Start by inspecting commit 83ea69d54bea72e1df9a2647ee101c73deb86d44 and how /usr/local/etc/php/conf.d/redis-session.ini is created. Reproduce the image using the non-root www-data user and verify that the Redis session handler can be configured without a permission error. Done means the image works with www-data and the Redis session handler remains available.