Release v20.41.4

Fixed

• A CommandValidator<> can now take a read model as a constructor dependency, resolved for the command's event source id — the same way a command's Handle() method receives it. Validators are now resolved from the command scope, so this no longer fails as it did when they were resolved from the root provider (throwing under scope validation or returning a stale instance).
• Using a read-model validator on the MVC controller path now raises a clear ReadModelValidatorRequiresCommandPipeline error pointing to the command pipeline, instead of an opaque dependency-resolution failure.