Check that `central_path` can be written to during SSH setup.

[JoeZiminski]

It is very easy to get the wrong path on the central server as it is often not obvious what the full path is. For example, on our hpc the full path is like /ceph/nfs/home/jzimiminski etc. and it is not always clear what the path should be. During 'setup ssh connection' it would be nice to have a new screen to a) confirm the full path of the central path relative to the server b) check you can actually write there. This has come up in user testing and is a priority.

[aakash-kharb]

After going through your suggestions, I have 2 approaches. In one, move the "check_write_permission" to utils/ssh.py and then assume user has input path correct. this remove the state of freeze. In another approach, I will try to merge "check_write_permission" with "_setup_rclone_central_ssh_config" . this may even remove the central path condition from setup_ssh_connection and move It to "_setup_rclone_central_ssh_config". Rest let's see how it goes.

[JoeZiminski]

Given the extension to AWS and Google Drive, the new-favourite approach is to use rclone to check permissions as it will work across all methods. It could be done after set up and raise a warning / error if permissions are not found. The approach could be:

rclone touch remote:path/.rclone_write_test

then

rclone delete remote:path/.rclone_write_test

[JoeZiminski]

This is now complete with #503 and introduction of the check_successful_connection_and_raise_error_on_fail function