[MU] SMIMECheckSignature integration tests and evolution

[chibenwa]

What

Write integration tests for SMIMECheckSignature within server/mailet/integration-testing/src/test/java/org/apache/james/mailets/crypto

Also I would like to get for each email processed the signature status as a header:

X-SMIME-Status: Good signature
X-SMIME-Status: Bad signature
X-SMIME-Status: Not signed

Adding the X-SMIME-Status would likely require code modifications within SMIMECheckSignature.

Why

MU governement asks for signature display in the webmail.

[chibenwa]

CF https://github.com/linagora/tmail-flutter/issues/3023

[chibenwa]

CF https://ci.linagora.com/linagora/lgs/twp/mail-gov-mauritius/-/issues/30

[chibenwa]

Dont forget to push a draft PR before the weekend nheee

[hungphan227]

draft pr https://github.com/apache/james-project/pull/2366