Cancellation of timeouts

[jmalloc]

This issue a place for discussion about how to (conceptually) cancel a pending timeout message. This is, by design, currently not an explicit feature. Instead, a timeout is canceled implicitly when the process that created it is ended.

The reasoning behind this decision is nuanced. The main influencing factors are:

1. The asynchronous/non-deterministic nature of message-based applications
2. The desire to encode domain logic using business language, as opposed to technical language, as much as possible
3. A desire to avoid "double handling" of timeout cancellation logic

I think we should have a verbal discussion about this, from which I will take some notes to include here and in an ADR. We can use our somewhat typical example of an invoicing system that using a timeout message to mark invoices as overdue.

/cc @koden-km

[jmalloc]

A question was raised in Slack about the progress of this issue, but the use case was solved by checking against the process' internal state. We will not make any related changes to Dogma at this time.