curl --request GET \
  --url https://app.dynamicauth.com/api/v0/sdk/{environmentId}/users/passkeys/signin \
  --header 'Authorization: Bearer <token>'

{
  "challenge": "An example name",
  "timeout": 123,
  "rpId": "An example name",
  "userVerification": "discouraged",
  "allowCredentials": [
    {
      "id": "<string>",
      "transports": [
        "usb"
      ]
    }
  ],
  "extensions": {
    "appid": "<string>",
    "appidExclude": "<string>",
    "credProps": true,
    "uvm": true
  },
  "hints": "hybrid"
}