Add more fine-grained ACLs for message listeners
Currently, a listener of an EventHub has access to all the messages within that EventHub. In the case of untrusted consumers (e.g. in a multi-tenant system), it's sometimes useful to restrict this permission to only read some of the messages in the EventHub.
A sample scenario is for using a shared Event Hub as a multi-tenant distributed log for a service. As it stands, each customer can already have their own publisher key to the shared Event Hub. It would also be nice if each customer can get a SAS key that only allows them to listen to messages from that publisher. This is currently not possible and so makes the idea of a multi-tenant Event Hub impossible.