Non-uppercase scheme parameter results in failed permissions checks

[bfin]

Currently, any lowercase or mixed case scheme parameter passed to JWTAuthenticationPolicy() will fail checks because _get_params() applies the upper() method to the request's scheme name but not to the custom scheme name, to which it is compared.

Example:
With scheme = 'Bearer', all of these headers currently fail auth:
Authorization: Bearer token="..."
Authorization: bearer token="..."
Authorization: BEARER token="..."
But with scheme = 'BEARER', they all pass.

As the most commonly used scheme is (probably) the mixed cased 'Bearer', it should probably not automatically fail...grin.