Remove ClientChannelView

[jtbandes]

Changelog

Rust: callbacks for on_client_advertise, on_client_unadvertise, and on_message_data now receive a &ClientChannel instead of a ClientChannelView.
Python: callback for on_client_advertise now receives a ClientChannel instead of a ChannelView; on_client_unadvertise and on_message_data now receive a client_channel_id instead of a ChannelView.

Docs

None

Description

Motivation: all the information about the client channel should be accessible to users in the callbacks.

Thoughts?

[eloff]

I like the change, it's how I originally wrote it and then changed my mind in the code review. I think the worry was exposing websocket protocol specific types in the callbacks, but those callbacks are very websocket and sometimes ros specific anyway.

For Python I see you opted not to expose the additional info other than the topic and id. We'll have to remember to come back and fix that. Unfortunately it all means allocating and copying in Python, there's no way around that - because Python is able to store a reference to ClientChannel in a way that escapes the callback. Rust cannot.

I think C and C++ have the same problems as Python, not sure how we deal with that there in performance may matter land. Maybe we give them a pointer or reference to an object with borrowed data (string_view or similar for c++?) and document that they have to copy it if they want to keep it after the callback returns.

[jtbandes]

Updated to expose the info to Python as well.

[bryfox]

I only took a quick look at the rust source since it'd been reviewed already, but this looks good to me.