Upgrade Microsoft.Graph to 5.x

[brian-pearson]

Current adapter is using 4.x

[mvdgun]

Hi @brian-pearson, thanks for reporting. I just assigned this one to the upcoming v1.2 release/milestone.

[mvdgun]

Moving to the v2.0 milestone since this change can be considered a breaking change. As soon as #6 lands we can more easily update client libraries since they are not part of the API surface anymore (abstracted away).