Add API key validation to Whisper ModelClient

- Added validation to ensure API key starts with 'sk-' prefix
- Follows the same pattern as other OpenAI ModelClients (GPT, DallE, Embeddings)
- Added comprehensive tests for API key validation

Author: OskarStark

src/platform/src/Bridge/OpenAi/Whisper/ModelClient.php

@@ -30,6 +30,9 @@ public function __construct(
         if ('' === $apiKey) {
             throw new InvalidArgumentException('The API key must not be empty.');
         }
+        if (!str_starts_with($apiKey, 'sk-')) {
+            throw new InvalidArgumentException('The API key must start with "sk-".');
+        }
     }
 
     public function supports(Model $model): bool

src/platform/tests/Bridge/OpenAi/Whisper/ModelClientTest.php

@@ -13,17 +13,48 @@
 
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\Attributes\Small;
+use PHPUnit\Framework\Attributes\TestWith;
 use PHPUnit\Framework\TestCase;
 use Symfony\AI\Platform\Bridge\OpenAi\Whisper;
 use Symfony\AI\Platform\Bridge\OpenAi\Whisper\ModelClient;
 use Symfony\AI\Platform\Bridge\OpenAi\Whisper\Task;
+use Symfony\AI\Platform\Exception\InvalidArgumentException;
 use Symfony\Component\HttpClient\MockHttpClient;
 use Symfony\Component\HttpClient\Response\MockResponse;
 
 #[CoversClass(ModelClient::class)]
 #[Small]
 final class ModelClientTest extends TestCase
 {
+    public function testItThrowsExceptionWhenApiKeyIsEmpty()
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The API key must not be empty.');
+
+        new ModelClient(new MockHttpClient(), '');
+    }
+
+    #[TestWith(['api-key-without-prefix'])]
+    #[TestWith(['pk-api-key'])]
+    #[TestWith(['SK-api-key'])]
+    #[TestWith(['skapikey'])]
+    #[TestWith(['sk api-key'])]
+    #[TestWith(['sk'])]
+    public function testItThrowsExceptionWhenApiKeyDoesNotStartWithSk(string $invalidApiKey)
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('The API key must start with "sk-".');
+
+        new ModelClient(new MockHttpClient(), $invalidApiKey);
+    }
+
+    public function testItAcceptsValidApiKey()
+    {
+        $modelClient = new ModelClient(new MockHttpClient(), 'sk-valid-api-key');
+
+        $this->assertInstanceOf(ModelClient::class, $modelClient);
+    }
+
     public function testItSupportsWhisperModel()
     {
         $client = new ModelClient(new MockHttpClient(), 'sk-test-key');