curl --request POST \
  --url https://api.digitalreceiptprotocol.org/api/v1/onboarding/generate-keys

{
  "success": true,
  "data": {
    "keyId": "a1b2c3d4-e5f6-4a7b-8c9d-0e1f2a3b4c5d",
    "publicKey": "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAz3...",
    "privateKey": "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQDP...",
    "algorithm": "RSA-OAEP-256"
  }
}