curl --request GET \
  --url https://api.firma.dev/functions/v1/signing-request-api/signing-requests/{id}/users \
  --header 'Authorization: <api-key>'

{
  "results": [
    {
      "id": "user123-e89b-12d3-a456-426614174000",
      "name": "Alice Johnson",
      "email": "alice@example.com",
      "first_name": "Alice",
      "last_name": "Johnson",
      "designation": "Signer",
      "order": 1,
      "finished_on": "2024-03-15T14:30:00Z",
      "declined_on": null,
      "decline_reason": null,
      "phone_number": "+1-555-0101",
      "street_address": null,
      "city": null,
      "state_province": null,
      "postal_code": null,
      "country": null,
      "title": "CEO",
      "company": "Acme Corp",
      "custom_fields": null,
      "required_fields": [
        "email",
        "first_name"
      ],
      "missing_fields": [],
      "required_read_only_fields": [],
      "ready_to_send": true
    },
    {
      "id": "user456-e89b-12d3-a456-426614174000",
      "name": "Bob Williams",
      "email": "bob@example.com",
      "first_name": "Bob",
      "last_name": "Williams",
      "designation": "Signer",
      "order": 2,
      "finished_on": null,
      "declined_on": null,
      "decline_reason": null,
      "phone_number": null,
      "street_address": null,
      "city": null,
      "state_province": null,
      "postal_code": null,
      "country": null,
      "title": null,
      "company": null,
      "custom_fields": null,
      "required_fields": [
        "email",
        "first_name",
        "phone_number"
      ],
      "missing_fields": [
        "phone_number"
      ],
      "required_read_only_fields": [
        {
          "variable_name": "contract_amount",
          "field_type": "number",
          "has_value": false
        }
      ],
      "ready_to_send": false
    }
  ]
}