Improve error handling

src/Client.php

@@ -245,6 +245,47 @@ private function handleResponse($response, $httpCode)
  throw new DeepLException($responseArray['message'], $httpCode);
  }
 
+/**
+ * @see https://www.deepl.com/docs-api/accessing-the-api/error-handling/
+ */
+switch ($httpCode) {
+case '400':
+throw new DeepLException('Bad request. Please check error message and your parameters.', $httpCode);
+break;
+
+case '403':
+throw new DeepLException('Authorization failed. Please supply a valid auth_key parameter.', $httpCode);
+break;
+
+case '404':
+throw new DeepLException('The requested resource could not be found.', $httpCode);
+break;
+
+case '413':
+throw new DeepLException('The request size exceeds the limit.', $httpCode);
+break;
+
+case '414':
+throw new DeepLException('The request URL is too long. You can avoid this error by using a POST request instead of a GET request, and sending the parameters in the HTTP body.', $httpCode);
+break;
+
+case '429':
+throw new DeepLException('Too many requests. Please wait and resend your request.', $httpCode);
+break;
+
+case '456':
+throw new DeepLException('Quota exceeded. The character limit has been reached.', $httpCode);
+break;
+
+case '503':
+throw new DeepLException('Resource currently unavailable. Try again later.', $httpCode);
+break;
+
+case '529':
+throw new DeepLException('Too many requests. Please wait and resend your request.', $httpCode);
+break;
+}
+
  if (!is_array($responseArray)) {
  throw new DeepLException('The Response seems to not be valid JSON.', $httpCode);
  }