Improve Integration Test Coverage

We now have reasonable coverage of different authentication mechanisms, we should try to get the missing methods covered, and get these tests to run across supported platforms.

### Windows
- [ ] Setup test run on Windows
- [ ] Investigate how to add users to a github actions runner.
- [ ] Run existing negotiate tests via the SSPI backend.
- [ ] Add a run with credentials via NTLM.

### Ubuntu, RHEL, OpenSUSE
- [ ] Investigate how to install the `[linux-kerberos]` extra.
- [ ] Investigate how to configure kerberos client.
- [ ] Add test run on these platforms.

### All platforms
- [ ] Research how we can test OIDC login flow
- [ ] Implement a set of OIDC tests including happy and sad paths