R1:885805f34067

Make Passphrase "token" credentials accessible via the API

Summary: Fixes T11867. This should really be on the `CredentialType` itself, but just punt that for now until the API endpoint gets updated. We'll need the actual code here anyway in some form.

Test Plan: {F1922728}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11867

Differential Revision: https://secure.phabricator.com/D16864