Add Schema::leaftypeName

Will be sued in the upcoming describe command.

Change-Id: I9ddecf8d3da1f82e8ce671210d51f31f895a9d27
diff --git a/src/static_schema.cpp b/src/static_schema.cpp
index 0eb564a..87d190a 100644
--- a/src/static_schema.cpp
+++ b/src/static_schema.cpp
@@ -305,3 +305,8 @@
 {
     throw std::runtime_error{"Internal error: StaticSchema::leafIsKey(std::string) not implemented. The tests should not have called this overload."};
 }
+
+std::optional<std::string> StaticSchema::leafTypeName([[maybe_unused]] const std::string& path) const
+{
+    throw std::runtime_error{"Internal error: StaticSchema::leafTypeName(std::string) not implemented. The tests should not have called this overload."};
+}