Update UploadSession to implement new IUploadSession interface

[andrueastman]

Changes proposed in this pull request

This PR updates UploadSession to implement IUploadSession to provide request builder compatibility with the LargeFileUploadTask work on this PR.

This should be merged in after the PR has been completed and deployed.

[andrueastman]

Build should succeed once the nuget package with the IUploadSession is out.

[darrelmiller]

[MIchaelMainer]

How to use the the v1.0 service library with the LargeFileUploadTask described in microsoftgraph/msgraph-sdk-dotnet-core#65

You can use your authenticated GraphServiceClient to get the uploadsession like this:

var uploadSession = await graphClient.Drive.Items["01KGPRHTV6Y2GOVW7725BZO354PWSELRRZ"]
                                                                       .ItemWithPath("_hamilton.png")
                                                                       .CreateUploadSession()
                                                                       .Request().PostAsync();
                    
LargeFileUploadTask<DriveItem> largeFileUploadTask = new LargeFileUploadTask<DriveItem>(uploadSession);

Subsequent steps will be the same.

[andrueastman]

You can also obtain an upload session for a FileAttachement like this

var attachement = new AttachmentItem
{
    Name = "Attachment.pdf",
    Size = fileStream.Length
};

var uploadSession = await graphClient.Me.Messages[messageId].Attachments.CreateUploadSession(attachement).Request().PostAsync();

LargeFileUploadTask<FileAttachment> largeFileUploadTask = new LargeFileUploadTask<FileAttachment>(uploadSession, fileStream);

Subsequent steps will be the same