Enable the user to set the target of the export file, e.g. external ressource #199
Description
If the user was able to set the target of the export file, one could directly export to the new instance or at least an external drive - e.g. via external resources. This would also solve the problem that one does always need twice the space to be able to export all the user data. Hence exporting from 450 GB user data from a 500 GB server to a new server with 1 TB space is currently not possible.
For importing one can choose the source already, so one can pick an external storage and there is no need to have twice the space in order to store the export file + unpack its content. For the latter a "consume mode" would be handy, but that's another issue.