Move EndpointListener interface out of the consumer implementation and into spec
Description
The EndpointListener packaged within the consumer module will be marked as deprecated in releases 0.9.x. This interface has been moved to the spec package. The consumer version will be completely removed in release 0.10.0
The EndpointListener packaged within the consumer module will be marked as deprecated in releases 0.9.x. This interface has been moved to the spec package. The consumer version will be completely removed in release 0.10.0