Complete MLflow integration implementation

- Implement mlflow.crewai.autolog() functionality as documented
- Add comprehensive event listener for crew, agent, and tool tracing
- Include proper error handling and graceful degradation
- Add full test coverage for MLflow integration
- Update PR description with implementation details

Addresses issue #2947 - MLflow integration now fully functional

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

tests/integrations/test_mlflow.py

@@ -0,0 +1,73 @@
+import pytest
+from unittest.mock import Mock, patch
+import sys
+
+from crewai.integrations.mlflow import autolog
+from crewai.utilities.events.third_party.mlflow_listener import mlflow_listener
+
+
+class TestMLflowIntegration:
+    
+    def test_autolog_without_mlflow_installed(self, caplog):
+        """Test autolog when MLflow is not installed"""
+        with patch.dict(sys.modules, {'mlflow': None}):
+            with patch('crewai.integrations.mlflow.mlflow', None):
+                autolog()
+                assert "MLflow is not installed" in caplog.text
+    
+    @patch('crewai.integrations.mlflow.mlflow')
+    def test_autolog_enable(self, mock_mlflow):
+        """Test enabling autolog"""
+        autolog()
+        assert mlflow_listener._autolog_enabled is True
+    
+    @patch('crewai.integrations.mlflow.mlflow')
+    def test_autolog_disable(self, mock_mlflow):
+        """Test disabling autolog"""
+        autolog(disable=True)
+        assert mlflow_listener._autolog_enabled is False
+    
+    @patch('crewai.integrations.mlflow.mlflow')
+    def test_autolog_silent_mode(self, mock_mlflow, caplog):
+        """Test silent mode suppresses logging"""
+        autolog(silent=True)
+        assert "MLflow autologging enabled" not in caplog.text
+    
+    @patch('crewai.integrations.mlflow.mlflow')
+    def test_mlflow_patching(self, mock_mlflow):
+        """Test that mlflow.crewai.autolog is available"""
+        from crewai.integrations.mlflow import _patch_mlflow
+        _patch_mlflow()
+        assert hasattr(mock_mlflow, 'crewai')
+        assert hasattr(mock_mlflow.crewai, 'autolog')
+
+    def test_reproduction_case_issue_2947(self):
+        """Test the exact case from issue #2947"""
+        with patch('crewai.integrations.mlflow.mlflow') as mock_mlflow:
+            mock_mlflow.tracing.start_span.return_value = Mock()
+            
+            import mlflow
+            mlflow.crewai.autolog()
+            
+            assert mlflow_listener._autolog_enabled is True
+            
+            from crewai import Agent, Task, Crew
+            
+            agent = Agent(
+                role="Test Agent",
+                goal="Test goal",
+                backstory="Test backstory"
+            )
+            
+            task = Task(
+                description="Test task",
+                expected_output="Test output",
+                agent=agent
+            )
+            
+            crew = Crew(
+                agents=[agent],
+                tasks=[task]
+            )
+            
+            assert crew is not None