ICS05: Allow application multiplexing on portID

[AdityaSripal]

With the advent of ICS30, many applications are already using a single port by forming a chain of ICS26 callbacks.

If we bring this behaviour into core IBC, by allowing multiple modules to register sequentially onto the port, we can reduce middleware complexity and allow for more custom behaviour.

Primarily, we may wish to allow packet data to contain data intended for multiple modules. This can get completely unmarshalled at the start and then passed through the different modules in a deterministic order.

[ethanfrey]

With the advent of ICS30, many applications are already using a single port by forming a chain of ICS26 callbacks.

I must admit I don't follow this repo closely, but I do understand IBC and the middleware (ICS30) design. I have not yet seen callbacks used (afaik, the callbacks for ICA is still not implemented) and don't understand the design pattern you are proposing here either.

Could you please link to a document on the design pattern this proposes and how it should work.
I mean, trivially I would think the ICS26 router owns the port and everyone else just registers on it, not on the port itself.

In general, I am afraid you are adding features people don't yet comprehend. While not adding features needed by many projects. Please clarify use cases (and users) before adding more such features. Especially if justified by "many applications are already using..."