Function format_create_aggregate_ddl 

fn format_create_aggregate_ddl(
    keyspace: &str,
    agg_name: &str,
    args_str: &str,
    state_func: &str,
    state_type: &str,
    final_func: Option<&str>,
    initcond: Option<&str>,
) -> String

Format a CREATE AGGREGATE DDL string.