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/flow/state_utils.py

@@ -1,111 +0,0 @@
-import json
-import uuid
-from datetime import date, datetime
-from typing import Any, Dict, List, Union
-
-from pydantic import BaseModel
-
-from crewai.flow import Flow
-
-SerializablePrimitive = Union[str, int, float, bool, None]
-Serializable = Union[
-    SerializablePrimitive, List["Serializable"], Dict[str, "Serializable"]
-]
-
-
-def export_state(flow: Flow) -> dict[str, Serializable]:
-    """Exports the Flow's internal state as JSON-compatible data structures.
-
-    Performs a one-way transformation of a Flow's state into basic Python types
-    that can be safely serialized to JSON. To prevent infinite recursion with
-    circular references, the conversion is limited to a depth of 5 levels.
-
-    Args:
-        flow: The Flow object whose state needs to be exported
-
-    Returns:
-        dict[str, Any]: The transformed state using JSON-compatible Python
-            types.
-    """
-    result = to_serializable(flow._state)
-    assert isinstance(result, dict)
-    return result
-
-
-def to_serializable(
-    obj: Any, exclude: set[str] | None = None, max_depth: int = 5, _current_depth: int = 0
-) -> Serializable:
-    """Converts a Python object into a JSON-compatible representation.
-
-    Supports primitives, datetime objects, collections, dictionaries, and
-    Pydantic models. Recursion depth is limited to prevent infinite nesting.
-    Non-convertible objects default to their string representations.
-
-    Args:
-        obj (Any): Object to transform.
-        exclude (set[str], optional): Set of keys to exclude from the result.
-        max_depth (int, optional): Maximum recursion depth. Defaults to 5.
-
-    Returns:
-        Serializable: A JSON-compatible structure.
-    """
-    if _current_depth >= max_depth:
-        return repr(obj)
-
-    if exclude is None:
-        exclude = set()
-
-    if isinstance(obj, (str, int, float, bool, type(None))):
-        return obj
-    elif isinstance(obj, uuid.UUID):
-        return str(obj)
-    elif isinstance(obj, (date, datetime)):
-        return obj.isoformat()
-    elif isinstance(obj, (list, tuple, set)):
-        return [
-            to_serializable(
-                item, max_depth=max_depth, _current_depth=_current_depth + 1
-            )
-            for item in obj
-        ]
-    elif isinstance(obj, dict):
-        return {
-            _to_serializable_key(key): to_serializable(
-                obj=value,
-                exclude=exclude,
-                max_depth=max_depth,
-                _current_depth=_current_depth + 1,
-            )
-            for key, value in obj.items()
-            if key not in exclude
-        }
-    elif isinstance(obj, BaseModel):
-        return to_serializable(
-            obj=obj.model_dump(exclude=exclude),
-            max_depth=max_depth,
-            _current_depth=_current_depth + 1,
-        )
-    else:
-        return repr(obj)
-
-
-def _to_serializable_key(key: Any) -> str:
-    if isinstance(key, (str, int)):
-        return str(key)
-    return f"key_{id(key)}_{repr(key)}"
-
-
-def to_string(obj: Any) -> str | None:
-    """Serializes an object into a JSON string.
-
-    Args:
-        obj (Any): Object to serialize.
-
-    Returns:
-        str | None: A JSON-formatted string or `None` if empty.
-    """
-    serializable = to_serializable(obj)
-    if serializable is None:
-        return None
-    else:
-        return json.dumps(serializable)