A number of our lua event handlers allow registering multiple
implementations to facilitate modular use.
For that to work, we must know ahead of the user lua call running
that any given handle is allowed to register multiple times. This is so
that we can report a meaningful error when incorrectly using a singleton
handler multiple times, and so that we can record a list of handlers
for the multiple case.
Prior to this commit, if we forgot to arrange to register the signature
as part of the context setup the consequence was that the event handler
would get registered as a singleton and when we went to call it, because
the signature is marked as allowing multiple but was not registered
as multiple, we would skate through and do nothing without reporting
an error because we assumed that the signature was registered
consistently.
In hindsight, that's a terrible idea because it results in silently
ignoring the registration issue, and not calling the event handler
at all.
This commit consolidates the multiple/single value resolution into
the same flow, then adds a check to confirm that we have a list
of handlers registered for the allow_multiple case, raising an
error otherwise that will hopefully encourage users to report
this problem to us if it manifests again in the future.
This commit includes fixing two event handlers that we missing
their signature registration.
One of them was broken anyway by being registered with a name
that didn't match the docs.
refs: https://github.com/KumoCorp/kumomta/issues/236
These allow performing arbitrary rate limiting operations
at both reception time and when messages are moved from the
scheduled queue and into the ready queue.
refs: https://github.com/KumoCorp/kumomta/issues/149
Wez Furlong