As part of REP-2011 (and by extension #1159), we want to expose the "inconsistent topic" callback from the DDS layer up into the client library layer. This will allow the client libraries to be notified when a topic with the same name, but different characteristics (namely topic field types) are in the graph.

As it stands today, only RTI Connext (and hence rmw_connextdds) fully implements this feature. Both Fast-DDS (and hence rmw_fastrtps) and CycloneDDS (and hence rmw_cyclonedds) allow one to register for the callback, but will never call it.

This tracking bug is meant to track both the request to upstream Fast-DDS and CycloneDDS to fully implement this feature, as well as be a central place to track the implementation of the callback within ROS 2.