Any documents with the same name existing in a directory that is copied to would cause an exception due to existing already, this fixes that by handling conflict resolution in those cases and automatically determining a file name that would avoid a conflict.
The URIs (Document ID + Root) of the Skyline `DocumentsProvider` was unoptimal as it wasn't relative to a base directory. This is required for opening a root without knowledge of the full path in advance, it is therefore cleaner to provide a uniform `ROOT_ID` in a companion class.
On Android 12 and above, files from an application's external storage directory cannot be accessed by the user. The only proper SAF-compliant way to solve this is to create a `DocumentProvider` which proxies access to internal storage accordingly.
