Amarok database update: comments welcome

[Tuomas Nurmi]

Hi again,

my database bug fixing merge request at
https://invent.kde.org/multimedia/amarok/-/merge_requests/134
starts to be quite ready.

I initially set out to fix bugs

https://bugs.kde.org/show_bug.cgi?id=426807 Out of range changedate prevents importing music folder (year 2038 problem) and

https://bugs.kde.org/show_bug.cgi?id=462268 Error storing podcast episode description in external MySQL database (non-full utf8)

and the merge request includes a commit that sets up some new tests for the specific bugs.
Additionally when fixing and testing, I encountered some similar-but-not-totally-related issues with
UTF8 characters and stored dates, and fixes for those are included as separate commits, too.

This would be the first database scheme update since 2012, so I thought I'll have to be pretty careful
and try asking around for any comments.

Should anyone be interested & brave enough to test, backing up database before you start is strongly recommended.
When using embedded database, it should be easy as
cp -r ~/.local/share/amarok/mysqle ~/.local/share/amarok/backupmysqle
and restoring backup should be possible by removing the updated mysqle dir and moving backupmysqle back in place.

I didn't test with my main external mysql collection yet, but everything seems pretty alright with my mysqle test setup,
so I'll try this with the external db a bit later.

Cheers
Tuomas