Fixed the payload generation

Author: Justin Hayes

src/Requests/Payload.php

@@ -49,7 +49,7 @@ protected function generateFromGuzzleRequest(GuzzleRequest $request) : string
             'method' => $this->request->getMethod(),
             'timestamp' => $timestamp,
             'uri' => (string) $this->request->getUri(),
-            'content' => $this->request->getBody()
+            'content' => $this->request->getBody()->getContents()
         ], JSON_UNESCAPED_SLASHES);
     }
 

tests/Requests/PayloadTest.php

@@ -31,7 +31,7 @@ public function it_translates_a_guzzle_request_to_a_json_encoded_string()
             'method' => $method,
             'timestamp' => $now,
             'uri' => $uri,
-            'content' => $request->getBody()
+            'content' => $request->getBody()->getContents()
         ], JSON_UNESCAPED_SLASHES);
 
         $this->assertEquals($expected, (string) new Payload($request));