Replace python-jose dependency

[Jipje]

A vulnerability has been found in the ecdsa dependency which will not be patched in the python-jose package. python-jose seems to be abandoned. Other people are also encountering these security issues.

I suggest to update authenticating-users/main.py to not use this insecure package. A commonly used alternative is PyJWT.

[Jipje]

Further searching also shows that GoogleCloudPlatform/python-docs-samples/iap/validate_jwt.py could contain a potential solution

[vchudnov-g]

Thanks for reporting this issue! We'll address it promptly.