[SFI compliance] Migrate service to service calls from SP to managed identity.

[danielscholl]

The impact of this project is greatly reduced if MS employees can’t use it without running in MS Tenant. Additionally, I’m receiving feedback that the EPAM solution has been struggling in customer tenants because policy issues. If we can make this SFI compliant, I expect we are much tighter now on security then the majority of customers where this was not the case before.