feat(core-flows): create or update payment collections in RMA flows (#8676)

* feat(core-flows): create or update payment collections in RMA flows

* chore: change ui to pick payment link from unpaid payment collection

* Apply suggestions from code review

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

* chore: fix mathbn

---------

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

packages/medusa/src/api/admin/payment-collections/validators.ts

@@ -12,6 +12,6 @@ export type AdminCreatePaymentCollectionType = z.infer<
 export const AdminCreatePaymentCollection = z
   .object({
     order_id: z.string(),
-    amount: z.number().optional(),
+    amount: z.number(),
   })
   .strict()