feat: add ability to set LLM for AgentPLanner on Crew (#1001)

* feat: add ability to set LLM for AgentPLanner on Crew

* feat: fixes issue on instantiating the ChatOpenAI on the crew

* docs: add docs for the planning_llm new parameter

* docs: change message to ChatOpenAI llm

* feat: add tests

src/crewai/utilities/planning_handler.py

@@ -1,5 +1,6 @@
-from typing import List, Optional
+from typing import Any, List, Optional
 
+from langchain_openai import ChatOpenAI
 from pydantic import BaseModel
 
 from crewai.agent import Agent
@@ -11,17 +12,27 @@ class PlannerTaskPydanticOutput(BaseModel):
 
 
 class CrewPlanner:
-    def __init__(self, tasks: List[Task]):
+    def __init__(self, tasks: List[Task], planning_agent_llm: Optional[Any] = None):
         self.tasks = tasks
 
-    def _handle_crew_planning(self) -> Optional[BaseModel]:
+        if planning_agent_llm is None:
+            self.planning_agent_llm = ChatOpenAI(model="gpt-4o-mini")
+        else:
+            self.planning_agent_llm = planning_agent_llm
+
+    def _handle_crew_planning(self) -> PlannerTaskPydanticOutput:
         """Handles the Crew planning by creating detailed step-by-step plans for each task."""
         planning_agent = self._create_planning_agent()
         tasks_summary = self._create_tasks_summary()
 
         planner_task = self._create_planner_task(planning_agent, tasks_summary)
 
-        return planner_task.execute_sync().pydantic
+        result = planner_task.execute_sync()
+
+        if isinstance(result.pydantic, PlannerTaskPydanticOutput):
+            return result.pydantic
+
+        raise ValueError("Failed to get the Planning output")
 
     def _create_planning_agent(self) -> Agent:
         """Creates the planning agent for the crew planning."""
@@ -32,6 +43,7 @@ class CrewPlanner:
                 "available to each agent so that they can perform the tasks in an exemplary manner"
             ),
             backstory="Planner agent for crew planning",
+            llm=self.planning_agent_llm,
         )
 
     def _create_planner_task(self, planning_agent: Agent, tasks_summary: str) -> Task: