Adds Redis cache (#4)

Requires adding a Redis host password through `redis_host_password`.

If you are updating you existing Nextcloud, you might have to manually update the `<nextcloud-data-volume>/config/config.php` and replace `memcache...` properties with:

```
  'memcache.distributed' => '\OC\Memcache\Redis',
  'memcache.local' => '\OC\Memcache\Redis',
  'memcache.locking' => '\OC\Memcache\Redis',
  'redis' => array(
     'host' => 'redis',
     'port' => 6379,
     ),
```

Co-authored-by: Jan Beilicke <dev@jotbe.io>
Reviewed-on: #4

tasks/main.yml

@@ -69,6 +69,17 @@
       SMTP_PASSWORD={{ smtp_password }}
       MAIL_FROM_ADDRESS={{ mail_from_address }}
       MAIL_DOMAIN={{ mail_domain }}
+      REDIS_HOST=redis
+      REDIS_HOST_PASSWORD={{ redis_host_password }}
+
+- name: Provide Redis env vars
+  copy:
+    dest: /home/{{ docker_user }}/nextcloud/redis.env
+    owner: "{{ docker_user }}"
+    group: "{{ docker_user }}"
+    mode: '0640'
+    content: |
+      REDIS_PASSWORD={{ redis_host_password }}
 
 - name: Provide restic-compose-backup env vars
   copy:

templates/docker-compose.nextcloud.yml.j2

@@ -25,12 +25,21 @@ services:
     container_name: nextcloud-app
     depends_on:
       - mysqldb
+      - redis
     volumes:
       - nextcloud:/var/www/html
       - /etc/localtime:/etc/localtime:ro
     env_file:
       - nextcloud.env
 
+  redis:
+    image: bitnami/redis:latest
+    restart: unless-stopped
+    volumes:
+      - redis:/data
+    env_file:
+      - redis.env
+
   web:
     image: nginx
     restart: always
@@ -85,6 +94,7 @@ services:
 
 volumes:
   mysqldb:
+  redis:
   nextcloud:
 {% if nextcloud_enable_restic_compose_backup %}
   backup-cache: