Refactor with dependency injection & protocol to allow for mock CL manager

Would be nice to make this middleware fully "testable" by using dependency injection & protocol (as was done for [AppLifecycleMiddleware](https://github.com/npvisual/AppLifecycleMiddleware/blob/166704b331159e32e2d81966b7ed9ba09ea96fd9/Sources/AppLifecycleMiddleware/AppLifecycleMiddleware.swift#L62)).

We can then inject a mock CoreLocationManager to control the expected test outcomes.