bug #805 Feature/treat nullable fields as required (HaKIMus)

This PR was squashed before being merged into the main branch.

Discussion
----------

 Feature/treat nullable fields as required

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes <!-- please update src/**/CHANGELOG.md files -->
| Docs?         | no <!-- required for new features -->
| Issues        | Fix #585 <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT

Context: #585 (comment)

Summary: Nullable fields must be present in the required list of their parent output structure, otherwise platforms (like openai) will reject the call.

Proof of work: #585 (comment)

`structured-output-union-types.php` output:
```php
file:///~/ai/examples/openai/structured-output-union-types.php#L33 Symfony\AI\Fixtures\StructuredOutput\UnionType\UnionTypeDtofile:///~/ai/fixtures/StructuredOutput/UnionType/UnionTypeDto.php#L14 {#310
  +time: Symfony\AI\Fixtures\StructuredOutput\UnionType\HumanReadableTimeUnionfile:///~/ai/fixtures/StructuredOutput/UnionType/HumanReadableTimeUnion.php#L14 {#316
    +readableTime: "2023-10-07T19:32:10Z"
  }
}
```

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Commits
-------

57d9b91  Feature/treat nullable fields as required

Author: chr-hertel

src/agent/tests/StructuredOutput/ResponseFormatFactoryTest.php

@@ -38,7 +38,7 @@ public function testCreate()
                         'isActive' => ['type' => 'boolean'],
                         'age' => ['type' => ['integer', 'null']],
                     ],
-                    'required' => ['id', 'name', 'createdAt', 'isActive'],
+                    'required' => ['id', 'name', 'createdAt', 'isActive', 'age'],
                     'additionalProperties' => false,
                 ],
                 'strict' => true,

src/platform/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 0.1
 ---
 
+ * Add nullables as required in structured outputs
  * Add support for Albert API for French/EU data sovereignty
  * Add unified abstraction layer for interacting with various AI models and providers
  * Add support for 16+ AI providers:

src/platform/src/Contract/JsonSchema/Factory.php

@@ -117,7 +117,9 @@ private function convertTypes(array $elements): ?array
                 if (!isset($schema['anyOf'])) {
                     $schema['type'] = [$schema['type'], 'null'];
                 }
-            } elseif (!($element instanceof \ReflectionParameter && $element->isOptional())) {
+            }
+
+            if (!($element instanceof \ReflectionParameter && $element->isOptional())) {
                 $result['required'][] = $name;
             }
 

src/platform/tests/Contract/JsonSchema/FactoryTest.php

@@ -183,7 +183,7 @@ public function testBuildPropertiesForUserClass()
                 'isActive' => ['type' => 'boolean'],
                 'age' => ['type' => ['integer', 'null']],
             ],
-            'required' => ['id', 'name', 'createdAt', 'isActive'],
+            'required' => ['id', 'name', 'createdAt', 'isActive', 'age'],
             'additionalProperties' => false,
         ];
 
@@ -304,7 +304,7 @@ public function testBuildPropertiesForUnionTypeDto()
                     ],
                 ],
             ],
-            'required' => [],
+            'required' => ['time'],
             'additionalProperties' => false,
         ];
 
@@ -347,7 +347,7 @@ public function testBuildPropertiesForExampleDto()
                     'enum' => ['Foo', 'Bar', null],
                 ],
             ],
-            'required' => ['name', 'taxRate'],
+            'required' => ['name', 'taxRate', 'category'],
             'additionalProperties' => false,
         ];