message: metrics service: static registration macro
  Description: Using to allow the metrics service to be used in a static library.
  Risk Level: low
  Testing: locally compiled and ran as static library
diff: #pragma once
  +#include "envoy/registry/registry.h"
  #include "envoy/server/instance.h"
  #include "server/configuration_impl.h"
  @@ -23,6 +24,8 @@ public:
  std::string name() override;
  };
  +DECLARE_FACTORY(MetricsServiceSinkFactory);
  +
  } // namespace MetricsService
  } // namespace StatSinks
  } // namespace Extensions
  