code: public <T extends MetricRegistryInstance> T create(MetricRegistryConstructor<T> constructor, EndpointRegistration api) {
          return create(constructor, () -> DateTime.now(DateTimeZone.UTC), api);
      }
docs: Creates a new MetricRegistryInstance.
  @param api The api with which to register configuration-specific endpoints.
  @return A metric registry instance, initialized based on this configuration.
  @throws RuntimeException if anything goes wrong during registration, for example the name is already in use.