curl --request POST \
  --url https://passkeys.hanko.io/{tenant_id}/registration/initialize \
  --header 'Content-Type: application/json' \
  --header 'apiKey: <apikey>' \
  --data '{
  "user_id": "<string>",
  "username": "<string>",
  "icon": "<string>",
  "display_name": "<string>"
}'

{
  "publicKey": {
    "rp": {
      "id": "<string>",
      "name": "<string>"
    },
    "user": {
      "id": "<string>",
      "displayName": "<string>",
      "name": "<string>"
    },
    "challenge": "<string>",
    "pubKeyCredParams": [
      {
        "type": "public-key",
        "alg": 123
      }
    ],
    "timeout": 123,
    "excludeCredentials": [
      {
        "type": "public-key",
        "id": "<string>",
        "transports": [
          "ble"
        ]
      }
    ],
    "authenticatorSelection": {
      "authenticatorAttachement": "cross-platform",
      "requireResidentKey": false,
      "residentKey": "discouraged",
      "userVerification": "discouraged"
    },
    "attestation": "direct",
    "extensions": {
      "appid": "<string>",
      "appidExclude": "<string>",
      "credProps": true
    }
  }
}