Пример обратного вызова Dropbox Sign

{
  "event": {
    "event_type": "signature_request_sent",
    "event_time": "1525470811",
    "event_hash": "e3f253402d44dcc16e5ecc5972e87c4ec32c0bb4027a130a5b700b7851ab74d1",
    "event_metadata": {
      "related_signature_id": null,
      "reported_for_account_id": "615266b89aeda4e8cd2f2a5d401dbc76f4fa",
      "reported_for_app_id": "ff3366f5236b94b4ded1aeecfc2"
    }
  },
  "account_guid": "615266b89aeda4e8cd2f2a5d401dbc76f4fa",
  "client_id": "ff3366f5236b94b4ded1aeecfc2",
  "signature_request": {
    "signature_request_id": "21bb8f947df4ad622c103f662543b230b713d",
    "test_mode": false,
    "title": "Signature Request Title",
    "original_title": "Original Signature Request Title",
    "subject": null,
    "message": "Please sign this document.",
    "metadata": {},
    "attachments": [
      {
        "id": "59c7ad1be6af226637c3d4dbfe4a801ff630e",
        "signer": 1,
        "name": "License",
        "instructions": "Add your license",
        "required": true,
        "uploaded_at": null
      }
    ],
    "is_complete": false,
    "is_declined": false,
    "has_error": false,
    "custom_fields": [],
    "response_data": [],
    "signing_url": null,
    "signing_redirect_url": null,
    "final_copy_uri": "/v3/signature_request/final_copy/21bb8f947df4ad622c103f662543b230b713d",
    "files_url": "https://api.hellosign.com/v3/signature_request/files/21bb8f947df4ad622c103f662543b230b713d",
    "details_url": "https://app.hellosign.com/home/manage?guid=21bb8f947df4ad622c103f662543b230b713d",
    "requester_email_address": "test@example.com",
    "signatures": [
      {
        "signature_id": "e53ed08286e83e421f061912a0cb1",
        "has_pin": false,
        "signer_email_address": "signer@example.com",
        "signer_name": "Signer One",
        "order": null,
        "status_code": "awaiting_signature",
        "signed_at": null,
        "last_viewed_at": null,
        "last_reminded_at": null,
        "error": null
      }
    ],
    "cc_email_addresses": []
  }
}