Refactor event base classes (#2491)

- Renamed `CrewEvent` to `BaseEvent` across the codebase for consistency
- Created a `CrewBaseEvent` that automatically identifies fingerprints for DRY
- Added a new `to_json()` method for serializing events

src/crewai/utilities/events/base_events.py

@@ -3,12 +3,26 @@ from typing import Any, Dict, Optional
 
 from pydantic import BaseModel, Field
 
+from crewai.utilities.serialization import to_serializable
 
-class CrewEvent(BaseModel):
-    """Base class for all crew events"""
+
+class BaseEvent(BaseModel):
+    """Base class for all events"""
 
     timestamp: datetime = Field(default_factory=datetime.now)
     type: str
     source_fingerprint: Optional[str] = None  # UUID string of the source entity
     source_type: Optional[str] = None  # "agent", "task", "crew"
     fingerprint_metadata: Optional[Dict[str, Any]] = None  # Any relevant metadata
+
+    def to_json(self, exclude: set[str] | None = None):
+        """
+        Converts the event to a JSON-serializable dictionary.
+
+        Args:
+            exclude (set[str], optional): Set of keys to exclude from the result. Defaults to None.
+
+        Returns:
+            dict: A JSON-serializable dictionary.
+        """
+        return to_serializable(self, exclude=exclude)