[Frontend] Implement Tool Calling with tool_choice='required' (#13483)

Signed-off-by: Liangfu Chen <liangfc@amazon.com>
Signed-off-by: Matt, Matthias <matthias.matt@tuwien.ac.at>
Co-authored-by: Liangfu Chen <liangfc@amazon.com>
Co-authored-by: mgoin <michael@neuralmagic.com>

tests/tool_use/test_chat_completion_request_validations.py

@@ -43,7 +43,8 @@ def test_chat_completion_request_with_no_tools():
     assert request.tool_choice == 'none'
 
 
-def test_chat_completion_request_with_tool_choice_but_no_tools():
+@pytest.mark.parametrize('tool_choice', ['auto', 'required'])
+def test_chat_completion_request_with_tool_choice_but_no_tools(tool_choice):
     with pytest.raises(ValueError,
                        match="When using `tool_choice`, `tools` must be set."):
         ChatCompletionRequest.model_validate({
@@ -54,7 +55,7 @@ def test_chat_completion_request_with_tool_choice_but_no_tools():
             'model':
             'facebook/opt-125m',
             'tool_choice':
-            'auto'
+            tool_choice
         })
 
     with pytest.raises(ValueError,
@@ -67,7 +68,7 @@ def test_chat_completion_request_with_tool_choice_but_no_tools():
             'model':
             'facebook/opt-125m',
             'tool_choice':
-            'auto',
+            tool_choice,
             'tools':
             None
         })