Comparing for equality doesn't work anymore since we removed a Task.
Simply check that all expected steps have been completed, regardless of
another task being completed as well.

It is now up to the user to request thumbnails generation.
It allows lazy loading, and prevents us from potentially generating
thousands of thumbnails for nothing when indexing an entire network
drive.

We now fallback to starting a playback early, no need for the old
complicated and full of special case code

is_present doesn't exist, and we want to reset the count for all tasks
anyway. It will start or not depending on the file presence, but we
don't need to care when reseting

This version will ensure all the File have an associated Task, to avoid
some content not appearing because it wasn't analyzed

This eases up recreating a task from a file, in case we failed to do so
during the original migration

Which is more appropriate for what this function does

It will now check for the folder existence & validity during the
Directory constructor. As such, we need to check for potential
exceptions being thrown, and don't need to check for the return value.

This will help us adjust the behavior when we can't find the filesystem
representation of a file

This prevents us from pushing the same file multiple times to the task
list, most likely in case we were to fail early during the discovery/parsing process

This is required if a service needs to fetch something from the
database, as we will mostly clear it after flush, causing dangling
reference to be held.

We were trying to re-create a file during each resume, which could only
work if the task got interrupted during the extraction step

Otherwise there is no way to enforce a rescan of failed tasks, or no
easy/efficient way to force a full rescan