Ordinary database engine is deprecated but there is no simple mean to change database engine to Atomic for existing databases.

Possible options:
- ALTER DATABASE MODIFY ENGINE query.
- Flag that triggers migration at ClickHouse startup.

The latter should be easier to implement. 

ContextPtr ,
        const String & ,
        const StoragePtr & ,
        const ASTPtr & )
    {
        throw Exception("There is no CREATE TABLE query for Database" + getEngineName(), ErrorCodes::NOT_IMPLEMENTED);
    }
    
    virtual void dropTable( 
        ContextPtr ,
        const String & ,
        [[maybe_unused]] bool sync = false)
    {
        throw Exception("There is no DROP TABLE query for Database" + getEngineName(), ErrorCodes::NOT_IMPLEMENTED);
    }
    
    
    
    virtual void attachTable(ContextPtr , const String & , const StoragePtr & , [[maybe_unused]] const String & relative_table_path = {}) 
    {
        throw Exception("There is no ATTACH TABLE query for Database" + getEngineName(), ErrorCodes::NOT_IMPLEMENTED);
    }
    
    virtual StoragePtr detachTable(ContextPtr , const String & )
    {
        throw Exception("There is no DETACH TABLE query for Database" + getEngineName(), ErrorCodes::NOT_IMPLEMENTED);
    }
    
    
    virtual void detachTablePermanently(ContextPtr , const String & )