Authenticate against Apigee

Add the ability to authenticate against Apigee.

I've also added an additional command to get the detail for a given card. This is mainly for testing purposes as I found that even a query for a single card by identifier against the develop instance of the Card API could cause timeouts.

For testing I'd advise using the staging apigee instance targeting the develop Card API (as we don't have a production deployment yet): https://devopsaccountrecoveryapigeestaging-eval-test.apigee.net/card-dev. Application credentials which can be added the cardclient's config are in 1Password.

The following command should then print the details of a card in the card-dev API:

python -m cardclient card-detail 7713f494-1559-48f7-9b6f-dc4dcbcc97c5

I've also added the ability to change the token url and to specify a bearer token directly. Both of these are undocumented as they are just included to allow for testing. The use of a bearer token can be tested by using the ./get_token.sh script in the deploy identity project and then setting the base_url to that of the development gcp cloud run instance.

I've also added the ability to specify the version of the API to use - with the current implementation defaulting to v1alpha1.

Closes #5 (closed)