Chaining several chain_callbacks in an overlay

[cehberlin]

Hi,
the following two lines are questionable in my opinion.

morse/src/morse/core/overlay.py

Line 40 in a64dcec

self.on_completion(result)

I am not sure if calling self.on_completion() in the chain_callback is correct. Why this is necessary? From my understanding the chain_callback can be used to trigger something when a service is completed. For this reason the function AbstractObject.completed() is checking on_completion. But why this is repeated in the executed chain_callback? The problem that I am in particular facing is, that this prevents to chain several chain_callbacks after each other or in other words chain several service calls after each other.

I have solved this for my use case by overwriting def _chain_callback in my overlay but just wanted to raise this issue to check if this might be a problem in general.