Support mixed for getContent method

As the Vectorizer currently makes assumptions about having to pass
string data to `PlatformInterface::invoke`, when that method can
actually take about any sort of input.

`Platform` implementations decide what data types they can handle
through their normalizers. Therefore, it should be up to `platform` to
handle types and not up to `store` to decide that it should only pass
strings.

Author: paulinevos

src/store/src/Document/EmbeddableDocumentInterface.php

@@ -15,7 +15,7 @@ interface EmbeddableDocumentInterface
 {
     public function getId(): mixed;
 
-    public function getContent(): string;
+    public function getContent(): mixed;
 
     public function getMetadata(): Metadata;
 }

src/store/src/Document/Vectorizer.php

@@ -18,12 +18,12 @@
 use Symfony\AI\Platform\Vector\Vector;
 use Symfony\AI\Store\Exception\RuntimeException;
 
-final readonly class Vectorizer implements VectorizerInterface
+final class Vectorizer implements VectorizerInterface
 {
     public function __construct(
-        private PlatformInterface $platform,
-        private string $model,
-        private LoggerInterface $logger = new NullLogger(),
+        private readonly PlatformInterface $platform,
+        private readonly string $model,
+        private readonly LoggerInterface $logger = new NullLogger(),
     ) {
     }
 
@@ -97,10 +97,13 @@ private function vectorizeString(string|\Stringable $string, array $options = []
     private function vectorizeEmbeddableDocument(EmbeddableDocumentInterface $document, array $options = []): VectorDocument
     {
         $this->logger->debug('Vectorizing embeddable document', ['document_id' => $document->getId()]);
+        $vectors = $this->platform->invoke($this->model, $document->getContent(), $options);
 
-        $vector = $this->vectorizeString($document->getContent(), $options);
+        if (!isset($vectors[0])) {
+            throw new RuntimeException('No vector returned for vectorization.');
+        }
 
-        return new VectorDocument($document->getId(), $vector, $document->getMetadata());
+        return new VectorDocument($document->getId(), $vectors[0], $document->getMetadata());
     }
 
     /**