//! Backend implementations for the Athena client.
/// # Gateway Backend
/// The Gateway backend is a backend that proxies requests to the Athena gateway.
/// It is used to execute queries on the Athena gateway.
/// It is also used to execute queries on the PostgreSQL backend.
/// It is also used to execute queries on the Scylla backend.
/// It is also used to execute queries on the Supabase backend.
/// The PostgreSQL backend is a backend that executes queries on the PostgreSQL database.
/// It is used to execute queries on the PostgreSQL database.
/// # Scylla Backend
/// The Scylla backend is a backend that executes queries on the Scylla database.
/// It is used to execute queries on the Scylla database.
/// # Supabase Backend
/// The Supabase backend is a backend that executes queries on the Supabase database.
/// It is used to execute queries on the Supabase database.