Added initial SFTP implementation using SSH.NET

[itsWindows11]

Resolved / Related Issues

To prevent extra work, all changes to the Files codebase must link to an approved issue marked as Ready to build. Please insert the issue number following the hashtag with the issue number that this Pull Request resolves.

• For Feature: Add support for SFTP #2407

Steps used to test these changes

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Currently waiting for #8974 to be implemented (since the current way of hooking filesystems to the UI is a total mess I cannot figure out) along with #15473, this PR is to lay the groundwork for resolving #2407 and will be marked as ready when everything is finished.

[0x5bfa]

This is around Storage Abstraction and it'll take a huge amount of time to get this abstraction ready for actual use.
@yaira2 we might as well merge like we have done as leave until finish.
If you agree, I'll take a look and leave a review.

[yaira2]

Sounds good

[0x5bfa]

LGTM otherwise!

You seem to have implemented for BaseStorageItem.
Is that working well?
If so, how did you validate/use SFTP storage?

[itsWindows11]

It's a draft for a reason 🙃 I'll do the testing outside of Files in a separate project, until I can figure out the UI part.

I've seen what's implemented for FTP support and tried to go for a similar implementation since it's pretty much the only non-shell-based storage implementation here with different protocols (AFAIK)

[yaira2]

@itsWindows11 what the status of this PR?

[0x5bfa]

Storage abstraction won't be implemented until the next year unless someone take over in Files and given OwlCore's progress. I think we should wrap up in order to merge.

[tmds]

Hi all, I wonder if you may be open to use Tmds.Ssh to implement this feature?

The SftpClient is fully async and it has methods that match well with what you need. Additionally, the upload/download methods are optimized to parallelize the transfer while keeping the overall .NET memory allocations low.

I'd be interested in any feedback you have while using the library.

[itsWindows11]

Sounds like a better option, but my SSH.NET issue regarding async IO support seems to be addressed so I don't think there's a need to switch.

The main blocker is the storage abstraction though, we either need to get this merged with switching the methods to be async and someone completes the integration, or wait until we can use OwlCore.Storage w/ extensions on the Files end.

[tmds]

@itsWindows11 the reason to consider switching could be performance. From the limited comparisons I did, Tmds.Ssh was considerably faster.