added missing provider handle

include/bedrock/ProviderHandle.hpp

@@ -0,0 +1,22 @@
+/*
+ * (C) 2020 The University of Chicago
+ *
+ * See COPYRIGHT in top-level directory.
+ */
+#ifndef __BEDROCK_PROVIDER_HANDLE_H
+#define __BEDROCK_PROVIDER_HANDLE_H
+
+#include <thallium.hpp>
+
+namespace bedrock {
+
+/**
+ * @brief A pointer to a ProviderHandle is returned by
+ * DependencyFinder::makeProviderHandle, wrapped as a
+ * std::shared_ptr<NamedDependency>.
+ */
+using ProviderHandle = thallium::provider_handle;
+
+} // namespace bedrock
+
+#endif