Added missing support for S/MIME envloped signing

Hi,

I have troubles getting the content of an email that is encrypted and signed (see attachment). The email itself only contains one smime.p7m attachment.

I use following code:

FileInputStream f = new FileInputStream(new File("email.eml"));

FileInputStream key = new FileInputStream(new File("keystore.p12"));
FileInputStream key2 = new FileInputStream(new File("keystore.p12"));

SmimeKeyStore smimeKeyStore = new SmimeKeyStore(key, "pw".toCharArray());
String alias = smimeKeyStore.getPrivateKeyAliases().iterator().next();

Pkcs12Config yourPkcs12Config = Pkcs12Config.builder()
        .pkcs12Store(key2) // path, File or InputStream
        .storePassword("pw")
        .keyAlias(alias)
        .keyPassword("pw")
        .build();

Email mergedEmail = EmailConverter.emlToEmail(f, yourPkcs12Config);
List<AttachmentResource> list = mergedEmail.getDecryptedAttachments();

for (AttachmentResource r : list) {
    play.Logger.info(r.readAllData());
}

But the output of r.readAllData() gives me binary data only.

When I open the email in Thunderbird it is decrypted correctly, it contains text only.

Can you please help me to get the actual content?
email.txt