Add cancellation token to hooks and pipeline bootstrap

[slaroche]

No description provided.

[isra17]

I'm not sure why we need the token to track cancellation instead of just handling the exception inside the hook that stop running the hooks and scope.

[isra17]

I'm not sure why we need the token to track cancellation instead of just handling the exception inside the hook that stop running the hooks and scope.

Another approach could be to add a cancel method or event (asyncio.Event) to ExecutableMessage/TopicMessage? This could be checked in the executor queue to not execute the message.

I had a use-case for this this morning where a RabbitMQ channel closing must cancel all its yielded messages.

[slaroche]

I'm not sure why we need the token to track cancellation instead of just handling the exception inside the hook that stop running the hooks and scope.

I wanted to do that initial, but not running the following hooks was ok, not running the scope function was trickier. I might be because I was trying to work just in the utils/hook.

I will the idea to handle it in the executor, I will try something.

Thanks for the feedback.

[slaroche]

I have a question:
if I catch and handle a CancelPipeline(Exception), is it important to close all the generators from on_call and on_results or I should just try to fail silently?

[slaroche]

@isra17 ready for review