PR #198 - see notes on that PR for more details on how to use the non-deprecated request and response.
This fixes the signature check for classes that handle the server notification validation and response that have been deprecated sine protocol V4 was released. These classes were never updated for protocol V4, and it seems have been used against protocol V3 for some time with no problems.
The new Opayo URLs are only in the protocol V4 release of this package, and people upgrading and still using the deprecated classes were finding it was breaking the notification. This fix will allow those deprecated classes to continue to be used as a quick workaround. I do recommend changing the way the notifications are received and responde to, however, in line with the README.
Many thanks to @Ferrisbane for this fix, and many apologies for not recognising what was happening for people reporting the 5006 error, since is was working for me and I could not reproduce the error - ducks.
