fix(SettlementTerm): open enum for acceptedPaymentMethods + add UPI, PAYMENT_URL

[ameetdesh]

Problem

acceptedPaymentMethods used additionalProperties: true on a type: string item to signal extensibility, but this is a no-op in JSON Schema — that keyword only applies to objects, not strings. Validators correctly enforced the two-value enum [CASH_DEPOSIT, BANK_TRANSFER] and rejected any extension values (e.g. "UPI").

Fix

Switch to the standard open-enum pattern using anyOf:

items:
  anyOf:
  - type: string
    enum: [CASH_DEPOSIT, BANK_TRANSFER, UPI, PAYMENT_URL]
  - type: string          # allows any extension value

This means:

• The known values are still documented and discoverable
• Any string not in the enum also passes validation (true extensibility)

New enum values

Value	When to use
UPI	Payment via UPI — pairs with payTo.vpa (e.g. "sellerplatform@hdfc")
PAYMENT_URL	Hosted checkout page — pairs with payTo.paymentUrl; gateway handles method selection

Relationship to payTo variants

payTo.accountNumber  →  acceptedPaymentMethods: ["BANK_TRANSFER"]
payTo.vpa            →  acceptedPaymentMethods: ["UPI"]
payTo.paymentUrl     →  acceptedPaymentMethods: ["PAYMENT_URL"] or multiple

🤖 Generated with Claude Code

[ravi-prakash-v]

@ameetdesh A better way would be to update this schema - https://github.com/beckn/schemas/blob/main/schema/AcceptedPaymentMethod/v2.0/attributes.yaml, and use a $ref in SettlementTerm to refer to this.

In fact it wouldn't hurt to alias this to just PaymentMethod instead of prefixing it with "Accepted" and deprecate it eventually.

If there are no schemas referring to this currently, we can directly do a rename and push.