Introduce a data_dir variable for tau

We've had too many confusions about the actual data directory and
unfortunately there are also inconsistencies. So use the data_dir
variable to mask host specific settings.

tau.yml

@@ -5,6 +5,8 @@
   vars:
     ansible_python_interpreter: /usr/bin/python3
 
+    data_dir: "/srv/docker"
+
     docker_registry_port: 5000 # this is the reg standard port
     docker_registry_domain: "docker.n39.eu"
 
@@ -75,7 +77,7 @@
 
     - name: Check if Docker Registry auth dir exists
       ansible.builtin.stat:
-        path: "/srv/docker/registry/auth"
+        path: "{{ data_dir }}/registry/auth"
       register: docker_dir
     - name: Fail if docker registry data dir does not exist
       ansible.builtin.fail:
@@ -84,7 +86,7 @@
     - name: Ensure the Docker Registry data directory exists
       # This may not be part of the backup
       file:
-        path: "/srv/docker/registry/data"
+        path: "{{ data_dir }}/registry/data"
         state: directory
 
     - name: Setup Docker Registry Container
@@ -102,8 +104,8 @@
           REGISTRY_AUTH_HTPASSWD_REALM: "Netz39 Docker Registry"
           REGISTRY_AUTH_HTPASSWD_PATH: "/auth/htpasswd"
         volumes:
-        - "/srv/docker/registry/data:/var/lib/registry:rw"
-        - "/srv/docker/registry/auth:/auth:rw"
+        - "{{ data_dir }}/registry/data:/var/lib/registry:rw"
+        - "{{ data_dir }}/registry/auth:/auth:rw"
 
     - name: Setup proxy site for the Docker Registry
       include_role:
@@ -115,7 +117,7 @@
 
     - name: Check if Dokuwiki data dir exists
       ansible.builtin.stat:
-        path: "/srv/docker/dokuwiki"
+        path: "{{ data_dir }}/dokuwiki"
       register: dokuwiki_dir
     - name: Fail if Dokuwiki data dir does not exist
       ansible.builtin.fail:
@@ -124,7 +126,7 @@
 
     - name: Set correct user for Dokuwiki data
       ansible.builtin.file:
-        path: "/srv/docker/dokuwiki"
+        path: "{{ data_dir }}/dokuwiki"
         owner: "1001"  # According to container config
         recurse: yes
 
@@ -141,7 +143,7 @@
         # env: No env here, because we copy the data
         # and the container will never be created from scratch.
         volumes:
-        - "/srv/docker/dokuwiki:/bitnami/dokuwiki:rw"
+        - "{{ data_dir }}/dokuwiki:/bitnami/dokuwiki:rw"
 
     - name: Setup proxy site for Dokuwiki
       include_role: