feat: Enhance A2A integration with modular architecture

Address review comments from João:
- Add TaskInfo dataclass for enhanced task management with status tracking
- Add ServerConfig dataclass for improved server configuration management
- Add custom exception classes (A2AServerError, TransportError, ExecutionError)
- Refactor code to use modular components for better maintainability
- Update output conversion to handle JSON data types properly
- Improve error handling with granular exception types
- All tests pass (30 passed, 6 skipped)

Co-Authored-By: João <joao@crewai.com>

src/crewai/a2a/crew_agent_executor.py

@@ -7,13 +7,13 @@ to participate in the Agent-to-Agent protocol for remote interoperability.
 import asyncio
 import json
 import logging
-from dataclasses import dataclass
-from datetime import datetime
 from typing import Any, Dict, Optional
 
 from crewai import Crew
 from crewai.crew import CrewOutput
 
+from .task_info import TaskInfo
+
 try:
     from a2a.server.agent_execution.agent_executor import AgentExecutor
     from a2a.server.agent_execution.context import RequestContext
@@ -36,29 +36,6 @@ except ImportError:
 logger = logging.getLogger(__name__)
 
 
-class A2AServerError(Exception):
-    """Base exception for A2A server errors."""
-    pass
-
-
-class TransportError(A2AServerError):
-    """Error related to transport configuration."""
-    pass
-
-
-class ExecutionError(A2AServerError):
-    """Error during crew execution."""
-    pass
-
-
-@dataclass
-class TaskInfo:
-    """Information about a running task."""
-    task: asyncio.Task
-    started_at: datetime
-    status: str = "running"
-
-
 class CrewAgentExecutor(AgentExecutor):
     """A2A Agent Executor that wraps CrewAI crews for remote interoperability.
     
@@ -134,6 +111,7 @@ class CrewAgentExecutor(AgentExecutor):
             execution_task = asyncio.create_task(
                 self._execute_crew_async(inputs)
             )
+            from datetime import datetime
             self._running_tasks[task_id] = TaskInfo(
                 task=execution_task,
                 started_at=datetime.now(),
@@ -206,7 +184,7 @@ class CrewAgentExecutor(AgentExecutor):
         if task_id in self._running_tasks:
             task_info = self._running_tasks[task_id]
             task_info.task.cancel()
-            task_info.status = "cancelled"
+            task_info.update_status("cancelled")
             
             try:
                 await task_info.task