OC_Util::setupFS($user) will create a data dir for the given string - no matter if the user really exists - OCP\JSON::checkUserExists($owner); introduces a ready to use check which will bail out with an JSON error

This reverts commit 6254f0a4.

When calling fopen() on some storage types, these return false instead
of throwing an exception.

This fix makes sure that in case the stream wasn't opened (for example
when a file doesn't exist any more) the stream isn't wrapped.

Also added 'rb' as another case that doesn't need to be wrapped.

Fixes #6832

The encrypted size was used when calculating folder sizes.
This fix now also sums up the unencrypted size and shows that one when
available.

This fixes the issue introduced by the transfer id which itself wasn't
taken into account by the shortcut code for part file in the shared
storage class.

Storage mount points are not deletable, so make sure that the unlink
operation and its hooks aren't run in such cases.

Note that some storages might recursively delete their contents when
calling unlink on their root. This fix prevents that as well.

Fixes #6526

in order to work properly with encryption ocTransferId is added to the file path - questionable usage of magic string