Module aggregation 

Aggregation functions and state management for event processing

This module provides aggregation capabilities including:

• Basic aggregations (count, sum, average, min, max)
• Complex aggregations (distinct, custom expressions)
• Aggregation state management

Structs

AggregationManager

Aggregation manager for handling multiple aggregations

Enums

AggregateFunction

Aggregation functions for window processing

AggregationState

Aggregation state for maintaining running calculations