Option to create .tar.7z archives in one step, due to 7zips limits in terms of file permissions

Hi,

I made very bad experiences concerning UNIX/macOS/precisely Mac OS X file permissions with 7zip first hand.
This got me in a lot of trouble, because I did not have the original files anymore and the unpacked files didn't have correct file permissions, which lead to all sorts of problems and a lot of pain.
As far as I know now, that is a general problem with 7zip, even in the reference implementation.
So all in all it is really not exaggerated to claim, that 7zip does not support file permissions. Most results in onlinesearches seem to agree.

Having learned from my mistakes, I now tar files I want to compress, then I compress them with 7z. So far, I did not run into problems (which is to be expected due to the nature of taring files).

Now, I think it would be very beneficial in terms of UX, to have Keka create .tar.7z files"automagically". That would save one step of work and even more clicks.

Really happy nonetheless, because it works fine doing this manually. Thanks for making this software, much appreciated.

Greetz