curl --request POST \
  --url https://api.dfns.io/auth/action/init \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "userActionServerKind": "Api",
  "userActionHttpMethod": "<string>",
  "userActionHttpPath": "<string>",
  "userActionPayload": "<string>"
}'

{
  "challenge": "<string>",
  "challengeIdentifier": "<string>",
  "rp": {
    "id": "<string>",
    "name": "<string>"
  },
  "supportedCredentialKinds": [
    {
      "kind": "Fido2",
      "factor": "first",
      "requiresSecondFactor": true
    }
  ],
  "userVerification": "required",
  "attestation": "none",
  "allowCredentials": {
    "key": [
      {
        "type": "public-key",
        "id": "<string>"
      }
    ],
    "passwordProtectedKey": [
      {
        "type": "public-key",
        "id": "<string>",
        "encryptedPrivateKey": "<string>"
      }
    ],
    "webauthn": [
      {
        "type": "public-key",
        "id": "<string>"
      }
    ]
  },
  "externalAuthenticationUrl": "<string>"
}