flatten the "playbooks" directory for better structure

Because of how Ansible local relative search paths work, the global
"files" and "templates" directories need to be next to the playbooks.
However its not intuitive to look into the playbooks directory to find
the files and templates for a host.
Therefore flatten the playbooks directory to get rid of this confusing
structure.

Also see:
https://docs.ansible.com/ansible/latest/playbook_guide/playbook_pathing.html#resolving-local-relative-paths

roles/dokuwiki/README.md

@@ -0,0 +1,49 @@
+# Role `dokuwiki`
+
+Makes sure that all required packages for a [DokuWiki](https://www.dokuwiki.org/dokuwiki) powered by php-fpm are installed.
+
+The DokuWiki tarball has to be unpacked to `/var/www/dokuwiki` (see variable below) manually afterwards.
+Please download it from https://download.dokuwiki.org.
+
+## Supported Distributions
+
+The following distributions are supported:
+
+- Debian 11
+
+## Required Arguments
+
+None.
+
+## Optional Argument
+
+- `dokuwiki__installpath`: Where your DokiWiki lives, default `/var/www/dokuwiki`
+- `dokuwiki__php_version`: Your PHP version, default `7.4`
+- `dokuwiki__php_user`: User of your php-fpm process, default `www-data`
+- `dokuwiki__nginx_user`: User of your nginx process, default `nginx`
+
+## nginx Configuration
+
+This role does not configure your nginx server.
+Please take a look at https://www.dokuwiki.org/install:nginx for a starting point.
+
+This role expects to work with our `nginx` role, which installs nginx from nginx's repo instead of Debian's package.
+This means, that nginx will not run as the `www-data`, which is used by php-fpm.
+
+So your `server` directive in the nginx configuration needs to use:
+```conf
+  root /var/www/dokuwiki;
+
+  [...]
+
+  location ~ \.php$ {
+    [...]
+    fastcgi_pass unix:/var/run/php/php-fpm-dokuwiki.sock;
+  }
+```
+
+
+## Updates
+
+This role doesn't handle updates.
+Please use the updater from Dokuwiki's admin interface to install updates.

roles/dokuwiki/defaults/main.yml

@@ -0,0 +1,5 @@
+---
+dokuwiki__installpath: "/var/www/dokuwiki"
+dokuwiki__php_version: "7.4"
+dokuwiki__php_user: "www-data"
+dokuwiki__nginx_user: "nginx"

roles/dokuwiki/files/mime.local.conf

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+# See here: https://www.dokuwiki.org/mime
+
+# Allow stl files.
+stl     !model/stl
+asc     application/pgp-keys

roles/dokuwiki/handlers/main.yml

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+- name: Restart php-fpm
+  become: true
+  ansible.builtin.systemd:
+    name: "php{{ dokuwiki__php_version }}-fpm.service"
+    state: restarted

roles/dokuwiki/meta/main.yml

@@ -0,0 +1,8 @@
+---
+dependencies:
+  - role: distribution_check
+    vars:
+      distribution_check__distribution_support_spec:
+        - name: Debian
+          versions:
+            - 11

roles/dokuwiki/tasks/main.yml

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+- name: Install php-fpm
+  become: true
+  ansible.builtin.apt:
+    name:
+      - php-fpm
+      - php-xml
+      - php-mbstring
+      - php-zip
+      - php-intl
+      - php-gd
+      - php-sqlite3
+  diff: false
+
+- name: Ensure `php-fpm` is enabled
+  become: true
+  ansible.builtin.systemd:
+    service: "php{{ dokuwiki__php_version }}-fpm.service"
+    enabled: true
+
+- name: Create custom php-fpm pool
+  become: true
+  ansible.builtin.template:
+    src: "{{ role_path }}/templates/php-fpm-dokuwiki.conf"
+    dest: "/etc/php/{{ dokuwiki__php_version }}/fpm/pool.d/dokuwiki.conf"
+    mode: "0755"
+  notify: Restart php-fpm
+
+- name: Create `/var/www` directory
+  become: true
+  ansible.builtin.file:
+    path: /var/www
+    state: directory
+    owner: "{{ dokuwiki__nginx_user }}"
+    group: "{{ dokuwiki__nginx_user }}"
+    mode: "0755"
+
+- name: Allow more mime types to be uploaded
+  become: true
+  ansible.builtin.copy:
+    src: mime.local.conf
+    dest: /var/www/dokuwiki/conf/mime.local.conf
+    owner: root
+    group: root
+    mode: "0644"

roles/dokuwiki/templates/php-fpm-dokuwiki.conf

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+[dokuwiki]
+user = {{ dokuwiki__php_user }}
+group = {{ dokuwiki__php_user }}
+listen = /var/run/php/php-fpm-dokuwiki.sock
+listen.owner = {{ dokuwiki__nginx_user }}
+listen.group = {{ dokuwiki__nginx_user }}
+php_admin_value[disable_functions] = exec,passthru,shell_exec,system
+php_admin_flag[allow_url_fopen] = on
+; Choose how the process manager will control the number of child processes. 
+pm = dynamic
+pm.max_children = 75
+pm.start_servers = 10
+pm.min_spare_servers = 5
+pm.max_spare_servers = 20
+pm.process_idle_timeout = 10s