sgID public keys

Example response

{
  "keys": [
    {
      "kty": "RSA",
      "kid": "g9DT_3W6OUaKCmjciEM0XNTsz6yTE1bBFec-xiN9zZk",
      "n": "rzz[...]tfbF3Q",
      "e": "AQAB",
      "use": "sig"
    }
  ]
}