[HttpClient] allow arbitrary JSON values in requests

Allow arbitrary values in the "json" request option. Previously values were
limitated to arrays and objects of type JsonSerializable. This doesn't account
for scalar values and classes with public properties (which don't need to
implement JsonSerializable), all of which are perfectly acceptable arguments to
json_encode.

Author: pschultz

CHANGELOG.md

@@ -15,6 +15,7 @@ CHANGELOG
  * added `TraceableHttpClient`, `HttpClientDataCollector` and `HttpClientPass` to integrate with the web profiler
  * allow enabling buffering conditionally with a Closure
  * allow option "buffer" to be a stream resource
+ * allow arbitrary values for the "json" option
 
 4.3.0
 -----

HttpClientTrait.php

@@ -332,18 +332,14 @@ private static function normalizePeerFingerprint($fingerprint): array
     }
 
     /**
-     * @param array|\JsonSerializable $value
+     * @param mixed $value
      *
      * @throws InvalidArgumentException When the value cannot be json-encoded
      */
     private static function jsonEncode($value, int $flags = null, int $maxDepth = 512): string
     {
         $flags = $flags ?? (JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_AMP | JSON_HEX_QUOT | JSON_PRESERVE_ZERO_FRACTION);
 
-        if (!\is_array($value) && !$value instanceof \JsonSerializable) {
-            throw new InvalidArgumentException(sprintf('Option "json" must be array or JsonSerializable, %s given.', \is_object($value) ? \get_class($value) : \gettype($value)));
-        }
-
         try {
             $value = json_encode($value, $flags | (\PHP_VERSION_ID >= 70300 ? \JSON_THROW_ON_ERROR : 0), $maxDepth);
         } catch (\JsonException $e) {

HttpOptions.php

@@ -86,7 +86,7 @@ public function setBody($body)
     }
 
     /**
-     * @param array|\JsonSerializable $json
+     * @param mixed $json
      *
      * @return $this
      */