Add invalid JSON to error message

If the schema parsing fails due to an error, add the actual JSON to the
error string. This helps solve any problems that might occur due to
malformed JSON on the sending end.

connectors/cdc-connector/cdc_connector.cpp

@@ -427,6 +427,8 @@ bool Connection::read_schema()
         {
             m_error = "Failed to parse JSON: ";
             m_error += err.text;
+            m_error += ". Data received so far: ";
+            m_error += row;
         }
     }