It allows us not to share connections between threads, and will do for
the time being.
It's quite unsafe, as TLS is used to store the connection, but doesn't
mark the connections as released.
This is mostly commited as such to move forward, we'll have to rewrite
the databases interactions in a near future
Now I'll be in the corner, crying.

Until our sqlite race condition is fixed

Apparently, some versionning defines are only present starting at a
specific version...

Use a more robust hack (or uglyness, actually) to wait for discoveries &
FS reloads.
This makes the folders tests green again!

We now only process one file at a time, as we do for snapshots.
The correct way would be to spawn more threads from the Parser class,
shall we want to process multiple items at once

Since the discovery will run in a thread, we can't assume results are
instantly available

failed test > sigsegv

This wrapper is responsible for stacking operations and running them in
a thread, rather than spawning a new std::thread each time

This removes the old std::string artist property on AlbumTrack