After bumping jest, the RSA signing performance went down by a factor of
2 or so, which causes tests to fail (since they went from ~3 seconds to
~6 seconds to generate a 4096-bit RSA signature). The tests generate
these signatures to fake responses from GitHub.
After replacing the keys with a 2048-bit key, the signing times are now
under a second.
* make "role" input optional
Per Vault documentation it doesn't have to be provided,
and the auth provider's "default_role" parameter is required
precisely for this case.
https://www.vaultproject.io/api/auth/jwt
