Sync not working against some WebDAV servers
As reported in opentodolist#444 (closed), the sync via the DirectorySynchronizer does not properly work against some WebDAV servers. It seems, some WebDAV implementations do not provide etags
for folders. This, however, it currently required for synchronization.
We should check if we can tweak the WebDAV classes such that a sync against such WebDAV servers is still possible (also it might be less efficient due to we have to run more queries in total).