Test against multiple versions/configurations of paperless

[VMelnalksnis]

Is your feature request related to a problem? Please describe.
Paperless API behavior has changed across versions, and also changes based on configuration (see PAPERLESS_TIME_ZONE).

Describe the solution you'd like
All integration tests are run against multiple combinations of versions and configurations.

Describe alternatives you've considered

Additional context
I could not find how to do this in XUnit without a ton of code duplication, most likely will have to move to NUnit. With NUnit I've already done something similiar, see https://github.com/VMelnalksnis/Gnomeshade/blob/master/tests/Gnomeshade.WebApi.Tests.Integration/Fixtures/WebserverTests.cs and https://github.com/VMelnalksnis/Gnomeshade/blob/master/tests/Gnomeshade.WebApi.Tests.Integration.PostgreSQL/WebserverSetup.cs