In other questions, I see responses saying that implementing a virtual file system is already possible in the SFTP server component: https://www.componentpro.com/qa/virtual-filesystem-sftp-component-netcore
However, I cannot find any documentation (or IntelliSense info) on the classes mentioned here. For example, `FileSystem` appears to be a namespace, not a type. There is the `ComponentPro.IO.FileSystem.FileSystemProvider` abstract type, but it only has one method and doesn't seem like it can be used at all.
Can you please provide documentation or a code example for to implement a custom file system provider, and how to make the `SftpSshServer` instance use it?