Support WebDAV (OwnCloud) checksum extension

[chris-1o]

Is your feature request related to a problem? Please describe.

Some firewalls only allow HTTP(S) traffic. In that case HTTP (WebDAV) is the only option to transfer files to SFTPGo.

SFTPGo currently already supports the X-OC-Mtime extension, but not the usage of checksums. Using a checksum would provide better file integrity guarantees.

Describe the solution you'd like

As a user I would like to use Rclone as a WebDAV client to transfer files to SFTPGo with an integrity check based on on-the-fly checksums.

Rclone-as-a-client already supports the Owncloud checksum mechanism.

Rclone-as-a-WebDAV-server implemented this mechanism too in: https://github.com/rclone/rclone/blob/177337686acce1686b860424ea04ca7a2d616950/cmd/serve/webdav/webdav.go#L518

Describe alternatives you've considered

No response

What are you using SFTPGo for?

Small business (3-person firm with file exchange?)

Additional context

No response