curl --request GET \
  --url https://api.luminpdf.com/v1/signature_request/{signature_request_id} \
  --header 'X-API-Key: <api-key>'

{
  "signature_request": {
    "signature_request_id": "<string>",
    "title": "<string>",
    "created_at": "<string>",
    "expires_at": "<string>",
    "details_url": "<string>",
    "signers": [
      {
        "email_address": "<string>",
        "name": "<string>",
        "group": 123,
        "is_approved": true
      }
    ],
    "updated_at": "<string>",
    "reason": "<string>"
  }
}