Allow subscriptions based not only on event type but also source

[berndtj]

Feature Request

Detailed Description

It would be nice to be able to use the source as a routing mechanism. For instance, I only want to subscribe to azure storage events from a particular storage account or container. Currently I can only subscribe to "Microsoft.Storage.BlobCreated".

I could change the event type in the event driver to allow for finer grained routing, but since we are standardized on cloud events, it makes sense that we could do something more generalized.

Context

Possible Implementation

Complexity

• [ ] Low - Simple enhancement or bug fix, no architectural changes or refactoring
• [x] Medium - Change requires some thought, but is relatively isolated
• [ ] High - Significant architectural change or large refactor

[kars7e]

I had a conversation with Mark around that, the spec says that only the eventType should be used for routing. Source is vendor-specific and defined as URI, it's not feasible to use it for routing at the top layer. Seems like the natural solution to this is creating a dedicated function that does the further routing (but we need to ensure a robust mechanism of emitting events from the function).