Update protected headers structure
* src/mail.cpp (Mail::buildProtectedHeaders_o): Update MIME part. (Mail::splitAndSend_o): Handle BCC split with protected headers. * src/mimedataprovider.cpp (MimeDataProvider::finalize): Improve parsing of headers. * src/mimemaker.cpp (write_part, add_body): Do not inject headers. (add_body_and_attachments): Do protected headers handling here. * src/recipientmanager.cpp (RecipientManager::isSplitByProtcol): Prepare API for protocol splits.
This uses a more robust way by adding a mime part for the
protected headers instead of injecting it in an exisiting mime
part.
- GnuPG-Bug-Id: T4858