Refactor ServiceRegistration and RegisterWithServiceRegistry

[TimMoore]

Lagom's development mode has two classes (for Scala and Java services) that implement registration with the service registry:

lagom/dev/service-registry/registration-javadsl/src/main/scala/com/lightbend/lagom/internal/server/ServiceRegistrationModule.scala

Lines 47 to 77 in 71b14a6

	/**
	* Automatically registers the service on start, and also unregister it on stop.
	*/
	@Singleton
	private class RegisterWithServiceRegistry @Inject() (
	lifecycle: ApplicationLifecycle,
	resolvedServices: ResolvedServices,
	config: ServiceConfig,
	registry: ServiceRegistry
	)(implicit ec: ExecutionContext) {
	private lazy val logger: Logger = Logger(this.getClass())
	private val locatableServices = resolvedServices.services.filter(_.descriptor.locatableService)
	lifecycle.addStopHook { () =>
	Future.sequence(locatableServices.map { service =>
	registry.unregister(service.descriptor.name).invoke().toScala
	}).map(_ => ())
	}
	locatableServices.foreach { service =>
	val c = ServiceRegistryService.of(config.url, service.descriptor.acls)
	registry.register(service.descriptor.name).invoke(c).exceptionally(new JFunction[Throwable, NotUsed] {
	def apply(t: Throwable) = {
	logger.error(s"Service name=[${service.descriptor.name}] couldn't register itself to the service locator.", t)
	NotUsed.getInstance()
	}
	})
	}
	}

lagom/dev/service-registry/devmode-scaladsl/src/main/scala/com/lightbend/lagom/internal/scaladsl/registry/ServiceRegistration.scala

Lines 17 to 45 in 71b14a6

	class ServiceRegistration(serviceInfo: ServiceInfo, lifecycle: ApplicationLifecycle, config: Config,
	registry: ServiceRegistry)(implicit ec: ExecutionContext) {
	private val logger: Logger = Logger(this.getClass)
	private val uri = {
	val httpAddress = config.getString("play.server.http.address")
	val httpPort = config.getString("play.server.http.port")
	URI.create(s"http://$httpAddress:$httpPort")
	}
	lifecycle.addStopHook { () =>
	Future.sequence(serviceInfo.locatableServices.map {
	case (service, _) => registry.unregister(service).invoke()
	}).map(_ => ())
	}
	serviceInfo.locatableServices.foreach {
	case (service, acls) =>
	registry.register(service)
	.invoke(ServiceRegistryService(uri, acls))
	.onComplete {
	case Success(_) =>
	logger.debug(s"Service name=[$service] successfully registered with service locator.")
	case Failure(e) =>
	logger.error(s"Service name=[$service}] couldn't register itself to the service locator.", e)
	}
	}
	}

These are very similar, but have some incidental differences, and some necessary differences due to the split javadsl and scaladsl APIs. They could be refactored to use the new ServiceRegistryClient abstraction, so that the common code can live in service-registry-client-core, and the necessary differences are encapsulated within the ServiceRegistryClient implementations.