IAS4SignalMessageConsumer: Add possibility to validate the signal (Signature)

[sopgreg]

Similiar to #162, it would be helpful to have a possibility to validate the Signal/Receipt received on the outgoing side, e.g. through the SignalMessageConsumer

Right now, the signature of IAS4SignalMessageConsumer#handleSignalMessage looks like this:

void handleSignalMessage (@Nonnull Ebms3SignalMessage aSignalMsg) throws Phase4Exception;

If the signature looked like this, it would be possible to check the message state for isSoapSignatureChecked/isSoapDecrypted:

void handleSignalMessage (@Nonnull Ebms3SignalMessage aSignalMsg, @Nonnull IAS4MessageState state) throws Phase4Exception;

Technically, this should be possible quite easily by changing the result of com.helger.phase4.servlet.AS4IncomingHandler#parseSignalMessage to return both the Ebms3SignalMessage and the IAS4MessageState and return this to the SignalMessageConsumer.

Looking forward to reading your opinion in this requirement.

[phax]

The IAS4SignalMessageConsumer and IAS4UserMessageConsumer APIs were extended. That's a backward incompatible change, that's why it is introduced in version 2.5.0.