Reject incoming updates when the channel is in registering or later phases

[manoranjith]

Context

Currently,

1. For outgoing updates, updateGeneric calls machine.Update, which in turn checks if machine is in Acting phase

2. For incoming updates, CheckUpdate is called, which in turn calls validTransition.

Problem

I think, this means an incoming update will be passed onto the user even when the channel is in registering or later phases. It will be upto the user of go-perun to check the phase and then reject this update.

Possible solution

In CheckUpdate, return error if phase of the registering or later phases.

[manoranjith]

@matthiasgeihs

[manoranjith]

@matthiasgeihs Do you think we should consider this for next release ?

[matthiasgeihs]

Seems relevant, we should consider it, for the upcoming, or alternatively for the next release. Is there a way to add optional items to a release?