SignupSentResponse

{
  "type": "object",
  "properties": {
    "next": {
      "type": "object",
      "properties": {
        "method": {
          "type": "string",
          "enum": [
            "POST"
          ],
          "description": "Always POST."
        },
        "url": {
          "type": "string",
          "description": "The verify call, absolute: POST it with { email, code } once the code arrives."
        }
      },
      "required": [
        "method",
        "url"
      ],
      "description": "The call that completes the signup."
    },
    "expires_in": {
      "type": "integer",
      "description": "Seconds the code stays valid, from the moment it was sent."
    }
  },
  "required": [
    "next",
    "expires_in"
  ]
}