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

tests/utilities/test_planning_handler.py

@@ -1,10 +1,11 @@
 from unittest.mock import patch
-from crewai.tasks.task_output import TaskOutput
 
 import pytest
+from langchain_openai import ChatOpenAI
 
 from crewai.agent import Agent
 from crewai.task import Task
+from crewai.tasks.task_output import TaskOutput
 from crewai.utilities.planning_handler import CrewPlanner, PlannerTaskPydanticOutput
 
 
@@ -28,7 +29,19 @@ class TestCrewPlanner:
                 agent=Agent(role="Agent 3", goal="Goal 3", backstory="Backstory 3"),
             ),
         ]
-        return CrewPlanner(tasks)
+        return CrewPlanner(tasks, None)
+
+    @pytest.fixture
+    def crew_planner_different_llm(self):
+        tasks = [
+            Task(
+                description="Task 1",
+                expected_output="Output 1",
+                agent=Agent(role="Agent 1", goal="Goal 1", backstory="Backstory 1"),
+            )
+        ]
+        planning_agent_llm = ChatOpenAI(model="gpt-3.5-turbo")
+        return CrewPlanner(tasks, planning_agent_llm)
 
     def test_handle_crew_planning(self, crew_planner):
         with patch.object(Task, "execute_sync") as execute:
@@ -40,7 +53,7 @@ class TestCrewPlanner:
                 ),
             )
             result = crew_planner._handle_crew_planning()
-
+            assert crew_planner.planning_agent_llm.model_name == "gpt-4o-mini"
             assert isinstance(result, PlannerTaskPydanticOutput)
             assert len(result.list_of_plans_per_task) == len(crew_planner.tasks)
             execute.assert_called_once()
@@ -72,3 +85,22 @@ class TestCrewPlanner:
         assert isinstance(tasks_summary, str)
         assert tasks_summary.startswith("\n                Task Number 1 - Task 1")
         assert tasks_summary.endswith('"agent_tools": []\n                ')
+
+    def test_handle_crew_planning_different_llm(self, crew_planner_different_llm):
+        with patch.object(Task, "execute_sync") as execute:
+            execute.return_value = TaskOutput(
+                description="Description",
+                agent="agent",
+                pydantic=PlannerTaskPydanticOutput(list_of_plans_per_task=["Plan 1"]),
+            )
+            result = crew_planner_different_llm._handle_crew_planning()
+
+            assert (
+                crew_planner_different_llm.planning_agent_llm.model_name
+                == "gpt-3.5-turbo"
+            )
+            assert isinstance(result, PlannerTaskPydanticOutput)
+            assert len(result.list_of_plans_per_task) == len(
+                crew_planner_different_llm.tasks
+            )
+            execute.assert_called_once()