Enable use of client directed sign ins with auth emulator

**Is your feature request related to a problem? Please describe.**
The auth emulation does not support the use of client directed sign ins, as described in the docs here: https://docs.microsoft.com/en-us/azure/app-service/configure-authentication-customize-sign-in-out#client-directed-sign-in

**Describe the solution you'd like**
If using the client directed sign in flow, the emulator should be able to behave in the same way as an app deployed on azure.
We should be able to use the emulator without having to make code changes compared to what we'd deploy on azure

**Describe alternatives you've considered**

**Additional context**