Better Exception Message for Missing Distributed DDL Configuration

Why it matters

This feature addresses the problem of unclear or unhelpful error messages that occur when the distributed DDL configuration is not set in ClickHouse. It provides users with better diagnostic information, making it easier to identify and resolve configuration issues related to distributed DDL.

How to use it

No specific action is required by users to enable this improvement. When the distributed DDL configuration is absent, ClickHouse will automatically display a clearer and more informative exception message to help users diagnose the problem.