//! Queue file saving functionality.
//!
//! Responsibilities:
//! - Serialize queue files to JSON with pretty formatting.
//! - Write queue files atomically to prevent corruption.
//!
//! Not handled here:
//! - Queue file loading or backup creation.
//! - Lock acquisition (assumed to be held by caller).
//!
//! Invariants/assumptions:
//! - Queue files are written atomically using `write_atomic`.
//! - Serialization should never fail for valid QueueFile structures.
use crateQueueFile;
use cratefsutil;
use ;
use Path;