Spport legacy cassettes. Create a recording index of 0 if no index key exists in the cassette.

Author: bwood

src/VCR/Cassette.php

@@ -30,6 +30,12 @@ public function playback(Request $request, int $index = 0): ?Response
  {
  foreach ($this->storage as $recording) {
  $storedRequest = Request::fromArray($recording['request']);
+
+ // Support legacy cassettes which do not have the 'index' key
+ if (!\array_key_exists('index', $recording)) {
+ $recording['index'] = 0;
+ }
+
  if ($index == $recording['index']) {
  if ($storedRequest->matches($request, $this->getRequestMatchers())) {
  return Response::fromArray($recording['response']);