Too strict type checking for Message type

[karptonite]

In AkismetMessage, setType requires $type to be MessageType. However, Akismet allows you to send any string for a message type, as detailed here.

For this reason, setType() should accept any string. We are running into this issue as we transition to this library because we use a custom message type in some cases.

Thanks for your work on this!

[curry684]

My apologies for the late response, missed this completely. We can fix this without B/C break by making the setters accept MessageType|string and converting it on the fly to store a string internally. We'd just need some magic in the getter to not break anything bad.

PR welcome or I'll pick it up later.

[curry684]

Implemented with full B/C.