curl --request POST \
  --url https://{projectId}.frontendapi.corbado.io/v2/me/passkeys/append/start \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "clientInformation": {
    "bluetoothAvailable": true,
    "clientEnvHandle": "<string>",
    "visitorId": "<string>",
    "canUsePasskeys": true,
    "isUserVerifyingPlatformAuthenticatorAvailable": true,
    "isConditionalMediationAvailable": true,
    "clientCapabilities": {
      "conditionalCreate": true,
      "conditionalMediation": true,
      "hybridTransport": true,
      "passkeyPlatformAuthenticator": true,
      "userVerifyingPlatformAuthenticator": true
    },
    "javaScriptHighEntropy": {
      "platform": "<string>",
      "platformVersion": "<string>",
      "mobile": true
    },
    "isNative": true,
    "webdriver": true,
    "privateMode": true,
    "clientEnvHandleMeta": {
      "ts": 123,
      "source": "ls"
    },
    "nativeMeta": {
      "platform": "<string>",
      "platformVersion": "<string>",
      "name": "<string>",
      "version": "<string>",
      "displayName": "<string>",
      "build": "<string>",
      "deviceOwnerAuth": "none",
      "isBluetoothAvailable": true,
      "isBluetoothOn": true,
      "isGooglePlayServices": true,
      "isDeviceSecure": true,
      "error": "<string>"
    }
  }
}'

{
  "newClientEnvHandle": "<string>",
  "appendNotAllowedReason": "passkey_already_exists",
  "attestationOptions": "{\"publicKey\":{\"challenge\":\"2m6...0w9/MgW...KE=\",\"rp\":{\"name\":\"demo\",\"id\":\"localhost\"},\"user\":{\"name\":\"example@mail.com\",\"id\":\"dXN...zk5\"},\"pubKeyCredParams\":[{\"type\":\"public-key\",\"alg\":-7},{\"type\":\"public-key\",\"alg\":-35},{\"type\":\"public-key\",\"alg\":-36},{\"type\":\"public-key\",\"alg\":-257},{\"type\":\"public-key\",\"alg\":-258},{\"type\":\"public-key\",\"alg\":-259},{\"type\":\"public-key\",\"alg\":-37},{\"type\":\"public-key\",\"alg\":-38},{\"type\":\"public-key\",\"alg\":-39},{\"type\":\"public-key\",\"alg\":-8}],\"authenticatorSelection\":{\"authenticatorAttachment\":\"platform\",\"requireResidentKey\":false,\"userVerification\":\"required\"},\"timeout\":60000,\"attestation\":\"none\"}}"
}