Fix Sharing "Expiration Date" on Oracle

This pull request ...
 - adds tests for Expiration Date for sharing with another user
 - adds tests for Expiration Date for sharing with another group
 - fixes sharing with Expiration Date on Oracle by changing the accepted date format
 - changes the date format accepted/returned by/from Oracle to "Y-m-d H:i:s" using `\Doctrine\DBAL\Event\Listeners\OracleSessionInit`
 - adds a test that ensures that databases accept timestamps in the format "Y-m-d H:i:s"
 - adds a test that ensures that databases return timestamps in the format "Y-m-d H:i:s"
 - replaces #4724

@bartv2 @DeepDiver1975 @ringmaster @schiesbn @icewind1991 @tanghus