Use protobuf PrintOptions if available (#1593)

Resolves #978

Author: Nevay

ProtobufSerializer.php

@@ -73,8 +73,8 @@ public function serialize(Message $message): string
         // @phpstan-ignore-next-line
         return match ($this->contentType) {
             ContentTypes::PROTOBUF => $message->serializeToString(),
-            ContentTypes::JSON => self::postProcessJsonEnumValues($message, $message->serializeToJsonString()),
-            ContentTypes::NDJSON => self::postProcessJsonEnumValues($message, $message->serializeToJsonString()) . "\n",
+            ContentTypes::JSON => self::serializeToJsonString($message),
+            ContentTypes::NDJSON => self::serializeToJsonString($message) . "\n",
         };
     }
 
@@ -92,16 +92,21 @@ public function hydrate(Message $message, string $payload): void
     }
 
     /**
-     * Workaround until protobuf exposes `FormatEnumsAsIntegers` option.
-     *
      * [JSON Protobuf Encoding](https://opentelemetry.io/docs/specs/otlp/#json-protobuf-encoding):
      * > Values of enum fields MUST be encoded as integer values.
      *
      * @see https://github.com/open-telemetry/opentelemetry-php/issues/978
      * @see https://github.com/protocolbuffers/protobuf/pull/12707
      */
-    private static function postProcessJsonEnumValues(Message $message, string $payload): string
+    private static function serializeToJsonString(Message $message): string
     {
+        // @phan-suppress-next-line PhanUndeclaredClassReference
+        if (\class_exists(\Google\Protobuf\PrintOptions::class)) {
+            /** @psalm-suppress TooManyArguments @phan-suppress-next-line PhanParamTooManyInternal,PhanUndeclaredClassConstant @phpstan-ignore arguments.count */
+            return $message->serializeToJsonString(\Google\Protobuf\PrintOptions::ALWAYS_PRINT_ENUMS_AS_INTS);
+        }
+
+        $payload = $message->serializeToJsonString();
         $pool = DescriptorPool::getGeneratedPool();
         $desc = $pool->getDescriptorByClassName($message::class);
         if (!$desc instanceof Descriptor) {