Get server context with custom token

[tusmester]

This story is part of an effort to make the following scenario simpler: the .Net client is used on a backend Asp.Net server to make server-to-server calls to a separate repository service.

The current server factory API assumes we always authenticate with the repository using configured (admin) clientid/secret values. There is a new scenario we need to support: when the user logs in on the client and makes a request to the custom backend API, and we need to make backend calls to a sensenet repository service from there in the name of the currently authenticated user.

• we want to get a server object without authentication
• because we already have a token that we want to set

Acceptance

• I can use the same or similar feature service registration API as in other cases (AddSenseNetRepository)
• get a server context using a similar API (GetServerAsync) and provide a custom auth token