added primary key resolver

source/core/object/primary_key_resolver.cpp

@@ -0,0 +1,8 @@
+#include "matador/object/primary_key_resolver.hpp"
+
+namespace matador::object {
+void primary_key_resolver::on_primary_key(const char *id, const std::string &pk, size_t /*size*/) {
+  primary_key_info_.column_name = id;
+  primary_key_info_.pk = pk;
+}
+}