Load management send slow down when close to limit

This is a copy of #248 with the two requested fixes added on top (255 as max byte and 65535 as max word).

The commits were actually made before I was aware of the new commit message rules, so the messages are still too long. Sorry about that…
Sounds reasonable. Currently we keep more detailed info though, hence it's a string. So you may need to have a separate Reason enum within the RejectReason being a proper object?