Here's the send-token function from https://github.com/jacobobryant/biff/blob/master/libs/tasks/resources/biff/template/src/%7B%7Bparent-path%7D%7D/routes/auth.clj#L40:
; To send login links via email, set MAILGUN_* in config/prod.env. Otherwise
; the links will only be printed to the console.
(defn send-token [{:keys [params/email
biff/base-url
mailgun/api-key
biff.auth/jwt-secret]
:as sys}]