{
  "summary": "Add subscriber to form by email address",
  "method": "POST",
  "path": "/v4/forms/{form_id}/subscribers",
  "tag": "Forms",
  "request_body": {
    "email_address": "string",
    "referrer": "string"
  },
  "response": {
    "subscriber": {
      "id": 1,
      "first_name": "string",
      "email_address": "string",
      "state": "active",
      "created_at": "string"
    }
  }
}