Add support easily passing additional Docker daemon options

Provoked by: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3247#issuecomment-2067207227

group_vars/matrix_servers

@@ -19,6 +19,14 @@
 # Also see `devture_docker_sdk_for_python_installation_enabled`.
 matrix_playbook_docker_installation_enabled: true
 
+matrix_playbook_docker_daemon_options: "{{ matrix_playbook_docker_daemon_options_auto | combine(matrix_playbook_docker_daemon_options_custom, recursive=True) }}"
+
+matrix_playbook_docker_daemon_options_auto:
+  experimental: "{{ devture_systemd_docker_base_ipv6_enabled }}"
+  ip6tables: "{{ devture_systemd_docker_base_ipv6_enabled }}"
+
+matrix_playbook_docker_daemon_options_custom: {}
+
 # Controls whether to attach Traefik labels to services.
 # This is separate from `devture_traefik_enabled`, because you may wish to disable Traefik installation by the playbook,
 # yet still use Traefik installed in another way.
@@ -483,13 +491,7 @@ devture_playbook_state_preserver_commit_hash_preservation_dst: "{{ matrix_base_d
 #                                                                      #
 ########################################################################
 
-docker_daemon_options: |
-  {{
-    {
-      'experimental': devture_systemd_docker_base_ipv6_enabled,
-      'ip6tables': devture_systemd_docker_base_ipv6_enabled,
-    }
-  }}
+docker_daemon_options: "{{ matrix_playbook_docker_daemon_options }}"
 
 ########################################################################
 #                                                                      #