* Create a scoped service provider for the call to Configure
- This allows scoped dependencies to be injected into the Configure method.
It means you can resolve the DbContext or any other scoped service without
the hassle of the CreateScope boiler plate. As a side effect, it also makes
Startup.Configure a bit more testable.
- Keep all the code in the test itself, instead of in an
extension method. Makes it easier to understand what's
happening without having to look up the extension
method's definition.
- Remove IStartupLoader and add `IStartup` instead that matches the signature hosting cares about
- Moved `UseStartup` to extension methods
- Move existing logic into `ConventionBasedStartup` class