Function map_handler 

pub async fn map_handler<T, U, F, Fut>(
    items: Vec<T>,
    func: F,
    state: &Arc<ExecutionState>,
    op_id: &OperationIdentifier,
    parent_ctx: &DurableContext,
    config: &MapConfig,
    logger: &Arc<dyn Logger>,
) -> Result<BatchResult<U>, DurableError>
where
    T: Serialize + DeserializeOwned + Send + Sync + Clone + 'static,
    U: Serialize + DeserializeOwned + Send + 'static,
    F: Fn(DurableContext, T, usize) -> Fut + Send + Sync + Clone + 'static,
    Fut: Future<Output = Result<U, DurableError>> + Send + 'static,

Executes a map operation over a collection with parallel processing.

This handler implements the map semantics:

• Creates a child context for each item
• Uses ConcurrentExecutor for parallel execution
• Supports ItemBatcher for batching
• Returns BatchResult with results for all items

Arguments

• items - The collection of items to process
• func - The function to apply to each item
• state - The execution state for checkpointing
• op_id - The operation identifier for the map operation
• parent_ctx - The parent DurableContext
• config - Map configuration
• logger - Logger for structured logging

Returns

A BatchResult containing results for all items.