AS-staging error. JSON parse error.

- If client sends an invalid authentication request then return the invalid response instead to crash.
I don't think removing try / catch to parse.json is a good idea, since this is the only way that we can check if html body request is valid.

Think if we get an status code 200 plus body contains something like:  <html>...</html>   --> JSON.parse will break.  So we should return bad request, which is 400 instead.