fix: properly encode JSON parameters

Author: faustbrian

src/API/AbstractAPI.php

@@ -132,7 +132,8 @@ protected function post(string $path, array $parameters = [])
     {
         $response = $this->connection->getHttpClient()->post(
             $this->getUri($path),
-            ['json' => $parameters]
+            [],
+            $this->createJsonBody($parameters)
         );
 
         return ResponseMediator::getContent($response);
@@ -149,4 +150,18 @@ private function getUri(string $path): string
     {
         return '/' !== $path[0] ? "/{$path}" : $path;
     }
+
+    /**
+     * Create a JSON encoded version of an array of parameters.
+     *
+     * @param array $parameters Request parameters
+     *
+     * @return null|string
+     */
+    protected function createJsonBody(array $parameters): ?string
+    {
+        return (count($parameters) === 0)
+            ? null
+            : json_encode($parameters, empty($parameters) ? JSON_FORCE_OBJECT : 0);
+    }
 }