Fixed #3330: Allow characters after final dot in filename

[Aniruddha-Deb]

This PR removes .pdf, .xopp and .xoj extensions (if any) and then appends xopp to the filename, rather than the simple replace_extension that was happening previously (because of which the text after the last dot in the filename was lost, as replace_extension used to replace that text thinking it was the extension).

Old code (in SaveJob::save)

fs::path const filepath = doc->getFilepath();
auto const target = fs::path{filepath}.replace_extension(".xopp");

New code:

fs::path filepath = doc->getFilepath();
Util::clearExtensions(filepath, ".pdf");
auto const target = fs::path{filepath}.concat(".xopp");

[personalizedrefrigerator]

This looks good to me! I can confirm that this fixes #3330.

[LittleHuba]

Could you check how this behaves with .xoj import/export? I do remember that we already touched this once because it did not work as expected.

[personalizedrefrigerator]

Could you check how this behaves with .xoj import/export? I do remember that we already touched this once because it did not work as expected.

Just checked: .xoj export/import still works with this change.

[personalizedrefrigerator]

Thank you for your work! I'm merging this in 24 hours unless there are objections.