Function build_postgres_kv_backend 

pub async fn build_postgres_kv_backend(
    store_addrs: &[String],
    cfg: Option<Config>,
    tls_config: Option<TlsOption>,
    schema_name: Option<&str>,
    table_name: &str,
    max_txn_ops: usize,
    auto_create_schema: bool,
) -> Result<KvBackendRef>

Builds a Postgres-backed metadata [KvBackendRef].

• store_addrs - Postgres connection URLs; only the first address is used.
• cfg - optional deadpool config to customize pool/session behavior.
• tls_config - optional TLS settings for the Postgres connection.
• schema_name - optional schema containing the metadata table.
• table_name - metadata KV table name.
• max_txn_ops - maximum operations allowed in one metadata transaction.
• auto_create_schema - whether to create schema_name when it is missing.