def seal(token, context = nil)
      raise RuntimeError, "signing private key must be set" unless self.instance_variable_get(:@signing_private_key)
      binary_token = token.to_binary_s
      signature = self.encryptor.sign(binary_token, self.instance_variable_get(:@signing_private_key), self, context)
      Base64.strict_encode64([binary_token, signature].join)
    end
def seal(token, context = nil)
      raise RuntimeError, "signing private key must be set" unless self.instance_variable_get(:@signing_private_key)
      binary_token = token.to_binary_s
      signature = self.encryptor.sign(binary_token, self.instance_variable_get(:@signing_private_key), self, context)
      Base64.strict_encode64([binary_token, signature].join)
    end
Signs the provided token and joins the data with the signature.

 token: a RecoveryToken instance

 returns a base64 value for the binary token string and the signature
 of the token.