Run tests on net462

[deleteLater]

We should run our tests on both net462 and net6.0, currently we only run these tests on net6.0.

featbit-dotnet-sdk/tests/FeatBit.ServerSdk.Tests/FeatBit.ServerSdk.Tests.csproj

Line 4 in 016f87b

<TargetFramework>net6.0</TargetFramework>

See #15

[krokofant]

I imagine the job needs to target the windows-latest runner and use the vstest-action. Since the test target is already net6.0 I understand that there might be compatibility issues if the target is changed as-is since unsupported APIs might be used in the test setup.

[deleteLater]

Yeah, to run the tests on net462, we do need to change some of the test code