safer port binding of etherpad docker container

don't bind to any host port if nginx_proxy is used
only bind to localhost if it's not used

group_vars/matrix_servers

@@ -765,6 +765,8 @@ matrix_dimension_database_password: "{{ matrix_synapse_macaroon_secret_key | pas
 
 matrix_etherpad_enabled: false
 
+matrix_etherpad_container_http_host_bind_port: "{{ '' if matrix_nginx_proxy_enabled else '127.0.0.1:9001' }}"
+
 matrix_etherpad_systemd_required_services_list: |
   {{
     ['docker.service']

roles/matrix-etherpad/defaults/main.yml

@@ -19,7 +19,7 @@ matrix_etherpad_user_gid: '5001'
 # Controls whether the matrix-etherpad container exposes its HTTP port (tcp/9001 in the container).
 #
 # Takes an "<ip>:<port>" or "<port>" value (e.g. "127.0.0.1:9001"), or empty string to not expose.
-matrix_etherpad_container_http_host_bind_port: '9001'
+matrix_etherpad_container_http_host_bind_port: ''
 
 # A list of extra arguments to pass to the container
 matrix_etherpad_container_extra_arguments: []