Back port the changes from #5560
Apply the access restrictions in the front end only (see #5603)
Correctly set the end date of duplicated events (see #5608)
Cherry-pick 'Fix the tooltip display in the repository module (see #5540)'
Purge the internal cache when disabling the Contao safe mode (see #5579)
Update the example website
Remove script tags when printing an article as PDF (see #5626)
Return the uploaded files in the upload widget (see #5631)
Correctly export the `pubDate` of calendar feeds (see #5641)
Preserve protocol relative URLs when minifying the HTML markup (see #5664)
Correctly reload or redirect upon Ajax requests (see #5647)