Add integration tests for Passwordless.AspNetCore

[Tyrrrz]

No description provided.

[Tyrrrz]

For parity with existing tests currently missing:

• Signin tests (requires Add support for the POST /signin/generate-token endpoint to generate a valid signin token #75)
• Add credential tests

[Tyrrrz]

@abergs this exceeded my timelimit allocated for finishing up tests. What do you think I should do with it in the current state?

The idea was to use a similar approach to testing Passwordless.AspNetCore as we currently do with Passwordless. It would wrap a dummy ASP.NET Core app with identity and test Passwordless endpoints to make sure they're working correctly (against a dockerized API).

The issue currently is that to reach full test parity, we need #75 and maybe something else. Also, I've uncovered a bug in the SDK in the process. On top of that, one test doesn't work and I'm not entirely sure why.

Currently, these tests are pretty valuable already as they verify a big chunk of the infra we have in Passwordless.AspNetCore, but they don't verify as much of the identity business logic as the previous tests did. Perhaps if we had proper coverage reporting, it would be easier to see the difference.