Pre-fill document type and number via API (prefilledFields)

Problem

Currently, prefilledFields.customer in the Payment Links API only supports: email, fullName, phoneNumber, countryCode, and language.

There's no way to pre-fill document type (typeIdNumber) and document number (idNumber) via the API payload. This forces merchants to use Custom JS workarounds with URL query parameters, which:

• Requires extra frontend development

• Is fragile and undocumented

• Doesn't work reliably across all scenarios
  

Use Case

When a customer completes checkout on our e-commerce platform, we already collect their document. We want to pass this data to Rebill to avoid asking the customer to re-enter it.

Proposed Solution
Add these fields to prefilledFields.customer

Benefits

• Reduces friction at checkout and improves conversion rates

• Consistent with how phone prefill works (recently added)

• No need for Custom JS workarounds