-callback sign(Message, Options, KTY) -> Signature
        when Message :: iodata(), Options :: any(), KTY :: any(), Signature :: iodata().

-callback signer(KTY, Fields) -> JWSMap when KTY :: any(), Fields :: map(), JWSMap :: map().

-callback verifier(KTY, Fields) -> [JWSALG] when KTY :: any(), Fields :: map(), JWSALG :: iodata().

-callback verify(Message, Options, Signature, KTY) -> boolean()
          when Message :: iodata(), Options :: any(), Signature :: iodata(), KTY :: any().