fix: Structured outputs for recursive models (#1311)

Handle recursive nature in the structured response_formats. 

Update test to include 1 nested model.

```
 LLAMA_STACK_CONFIG=dev pytest -s -v tests/client-sdk/inference/test_text_inference.py --inference-model "openai/gpt-4o-mini" -k test_text_chat_completion_structured_output
```

---------

Co-authored-by: Ashwin Bharambe <ashwin.bharambe@gmail.com>

tests/client-sdk/inference/test_text_inference.py

@@ -4,6 +4,7 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+
 import pytest
 from pydantic import BaseModel
 
@@ -342,11 +343,15 @@ def test_text_chat_completion_with_tool_choice_none(client_with_models, text_mod
     ],
 )
 def test_text_chat_completion_structured_output(client_with_models, text_model_id, test_case):
+    class NBAStats(BaseModel):
+        year_for_draft: int
+        num_seasons_in_nba: int
+
     class AnswerFormat(BaseModel):
         first_name: str
         last_name: str
         year_of_birth: int
-        num_seasons_in_nba: int
+        nba_stats: NBAStats
 
     tc = TestCase(test_case)
 
@@ -364,7 +369,8 @@ def test_text_chat_completion_structured_output(client_with_models, text_model_i
     assert answer.first_name == expected["first_name"]
     assert answer.last_name == expected["last_name"]
     assert answer.year_of_birth == expected["year_of_birth"]
-    assert answer.num_seasons_in_nba == expected["num_seasons_in_nba"]
+    assert answer.nba_stats.num_seasons_in_nba == expected["num_seasons_in_nba"]
+    assert answer.nba_stats.year_for_draft == expected["year_for_draft"]
 
 
 @pytest.mark.parametrize("streaming", [True, False])