check_environment_vars/0 displays a friendly error message if the AUTH_API_KEY environment variable is not defined.

get_baseurl_from_conn/1 derives the base URL from the conn struct e.g: http://localhost:4000 or https://app.dwyl.com

strip_struct_metadata/1 removes the Ecto Struct metadata from a struct. This is essential before attempting to create a JWT as Jason.encode/2 chokes on any invalid data. See: github.com/dwyl/auth_plug/issues/16