fix(tests): complete Model struct initialization for issue Michael-A-Kuykendall#113

- Add missing optional fields (permission, root, parent) to all Model test initializations
- Fixes compilation errors in test_models_response_structure and test_openai_response_structures
- All 24 openai_compat tests now passing
- Ensures regression test for Open WebUI/AnythingLLM compatibility works correctly

Completes fix for Issue Michael-A-Kuykendall#113

Signed-off-by: Michael A. Kuykendall <michaelallenkuykendall@gmail.com>

Author: Michael-A-Kuykendall

src/openai_compat.rs

@@ -689,12 +689,18 @@ mod tests {
                     object: "model".to_string(),
                     created: 1234567890,
                     owned_by: "shimmy".to_string(),
+                    permission: None,
+                    root: None,
+                    parent: None,
                 },
                 Model {
                     id: "model2".to_string(),
                     object: "model".to_string(),
                     created: 1234567890,
                     owned_by: "shimmy".to_string(),
+                    permission: None,
+                    root: None,
+                    parent: None,
                 },
             ],
         };
@@ -1006,12 +1012,18 @@ mod tests {
                     object: "model".to_string(),
                     created: 0,
                     owned_by: "shimmy".to_string(),
+                    permission: None,
+                    root: None,
+                    parent: None,
                 },
                 Model {
                     id: "test-model-2".to_string(),
                     object: "model".to_string(),
                     created: 0,
                     owned_by: "shimmy".to_string(),
+                    permission: None,
+                    root: None,
+                    parent: None,
                 },
             ],
         };