monitoring.filebeat: allow additional volumes

monitoring.filebeat/templates/docker-compose.yml.j2

@@ -10,6 +10,11 @@ services:
       - /var/run/docker.sock:/var/run/docker.sock:ro
       - ./filebeat.yml:/usr/share/filebeat/filebeat.yml:ro
       - ./modules.d:/usr/share/filebeat/modules.d:ro
+{% if filebeat is defined and filebeat.docker is defined }
+{% for volume in filebeat.docker.additional_volumes | default([]) %}
+      - {{ volume }}
+{% for %}
+{% if %}
     restart: unless-stopped
     logging:
       driver: json-file