[Dev] Support SMime signature validation

[dab246]

Descriptions

• Issue: #3023

DoD

• [ ] Add a good/bad signature icon is displayed next to the email

• [ ] Show tooltip message when hover icon:

  • If X-SMIME-Status: Good signature tooltip message is The authenticity of this message had been verified with SMime signature
  • If X-SMIME-Status: Bad signature tooltip message is This message failed SMime signature verification.

• [ ] Check on offline mode

Technical

• Get X-SMIME-Status in headers property of email. With name = X-SMIME-Status.
• Create enum SMimeSigantureStatus:

enum SMimeSigantureStatus {
   goodSignature,
   badSignature,
   notSigned
}

• In EmailExtension add:

static const String smimeSignatureStatusHeaderName = 'X-SMIME-Status';

SMimeSigantureStatus get smimeSignatureStatus {
    final smimeStatus = headers?.firstWhereOrNull((header) => header.name == smimeSignatureStatusHeaderName);
    if (smimeStatus == 'Good signature') {
       return SMimeSigantureStatus.goodSignature;
    } else  if (smimeStatus == 'Bad signature') {
       return SMimeSigantureStatus.badSignature;
    } else {
      return SMimeSigantureStatus.notSigned;
    }
}

• Add good/bad siganture icon in InformationSenderAndReceiverBuilder widget

[hoangdat]

• [ ] unit test
• [ ] widget test