FTPFileProvider: copyItem's overwrite flag does not work

[rsnitsch]

Calling

ftpProvider.copyItem(localFile: first.url, to: remotePath, overwrite: true)

fails if the remote file already exists. In FTP, you have to delete existing remote files. Overwriting is not possible.

Therefore, the expected behavior for overwrite: true is that FTPFileProvider checks file existence first, when overwrite flag is true, and then deletes the remote file if necessary, before proceeding with the actual upload.