Feature request

Current state

Parameters are using a separator different than '/' to avoid ambiguity between nodes and parameters belonging to a node (see parameter design document for rationale and example).
This separator is currently hard coded and implemented in c++ only.

Feature description

We should implemented so that it is be available for any downstream package regardless of its' language.

Implementation considerations

We could declare this separator in a single place by defining it as a constant in one of the rcl_interfaces dedicated to parameters or create a new message for this. It has the advantage of being consumable by any language that has a rosidl generator, but can be considered overkill to declare a message just for this.

Alternative suggestions are welcome