BUG: 431218
FIXED-IN: 5.16.3

The release/20.08 branch is not released anymore, but used in Debian,
only cherry-picked patches will be added to the release branch.

FIX[messagecomposer/cryptocomposertests]: Use EncryptJob exec instead of async variant to pass tests.

If there is a signed part we should have the protected headers there
instead of only the encrypted part.

When dealing with encryption and protected headers it is enough to
reference the headers in the messagepart, as the result is encrypted
directly. This is different for Sign only and there may be jobs after
signing that are changing the mail headers, so we need to copy all
headers into the encapsulated part instead of referencing them.

BUG: 427091
FIXED-IN: 5.16.1

Tested on local machine to run this without #if and it was successful.

gpg does not import keys to new kbx format, so we need to do this by
hand.

If ContactPreferences are set explitly and not loaded via Akonadi this
function cannot lock. So it is safe to move the #if.