Not quite sure if this is considered a dokuwiki or php-fpm packaging problem.

Description:

Trying to run the dokuwiki installer with php-fpm fails with

```
The installer found some problems, indicated below. You can not continue
until you have fixed them.

{DOCUMENT_ROOT}/conf/ is not writable by DokuWiki. You need to fix the
permission settings of this directory!
```

The dokuwiki config directory is located at `/etc/webapps/dokuwiki/.

The php-fpm7.service specifies `ProtectSystem=full`, which disallows writes to `/etc`

Additional info:
* php7-fpm 7.4.27-1
* nginx 1.20.2-1
* Dokuwiki installed with nginx as described in the wiki

Steps to reproduce:

* Fresh Arch
* install nginx, php7-fpm, dokuwiki
* Edit nginx config as in the wiki (nginx.conf attached)
* start nginx, php-fpm
* open http://localhost:80/install.php in a browser

Attached is a Vagrant file that automates those steps.


Solutions:

* (Really Bad) Don't use `ProtectSystem=full` in php-fpm
* (Mediocre) Ship php-fpm with `ReadWritePaths=/etc/webapps/`
* (Good) Ship dokuwiki with a systemd service dropin like

```
#/etc/systemd/system/php-fpm7.service.d/dokuwiki.conf
[Service]
ReadWritePaths=/etc/webapps/dokuwiki/
```