curl --request POST \
  --url https://staging.crossmint.com/api/2025-06-09/wallets/{walletLocator}/signatures \
  --header 'Content-Type: application/json' \
  --header 'X-API-KEY: <x-api-key>' \
  --data '
{
  "type": "message",
  "params": {
    "message": "Hello, world!",
    "signer": "external-wallet:0xB17Ea8d34078424B9d7D126E444d5F2C3CC5c81E",
    "chain": "ethereum"
  }
}
'

{
  "id": "<string>",
  "params": {
    "message": "<string>",
    "signer": {
      "address": "<string>",
      "locator": "<string>"
    }
  },
  "approvals": {
    "pending": [
      {
        "signer": {
          "address": "<string>",
          "locator": "<string>"
        },
        "message": "<string>"
      }
    ],
    "submitted": [
      {
        "signature": "<string>",
        "submittedAt": 123,
        "signer": {
          "address": "<string>",
          "locator": "<string>"
        },
        "message": "<string>",
        "metadata": {
          "deviceInfo": "<string>",
          "ipAddress": "<string>",
          "userAgent": "<string>"
        }
      }
    ],
    "required": 123
  },
  "createdAt": 123,
  "completedAt": 123,
  "error": "<unknown>",
  "outputSignature": "<string>"
}