Ensure auth tests support gzipped responses

[nickevansuk]

To successfully display gzipped auth responses, we must decompress the gzipped string to get the actual response content.

Hints for achieving this can be found here: https://chat.openai.com/share/657aeac0-097b-4502-8be6-566aa40abba7.

Consider updating the hosted Reference Implementation to implement GZip (if it doesn't already; likely possible by configuring Azure) such that this can be tested.