fix: respect customUiRoute configuration in test provider

The test provider's customUiRoute parameter was being ignored when
generating checkout URLs. The checkout URL was always using the
hardcoded API endpoint instead of the configured custom UI route.

This fix ensures that when customUiRoute is configured, the generated
checkoutUrl will use the custom route (e.g., /test-payment/:id)
instead of the default API route.

Fixes issue where test provider checkout URLs returned 404 errors
because they pointed to /api/payload-billing/test/payment/:id instead
of the configured custom UI route.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@xtr-dev/payload-billing",
-  "version": "0.1.16",
+  "version": "0.1.19",
   "description": "PayloadCMS plugin for billing and payment provider integrations with tracking and local testing",
   "license": "MIT",
   "type": "module",

src/collections/hooks.ts

@@ -7,7 +7,8 @@ export const initProviderPayment = async (payload: Payload, payment: Partial<Pay
 
   if (!billing) {
     throw new Error(
-      'Billing plugin not initialized. Make sure the billingPlugin is properly configured in your Payload config and that Payload has finished initializing.'
+      'Billing plugin not initialized. Make sure the billingPlugin is properly configured in your Payload config and that Payload has finished initializing. ' +
+      'If you are calling this from a Next.js API route or Server Component, ensure you are using getPayload() with the same config instance used in your Payload configuration.'
     )
   }
 

src/collections/payments.ts

@@ -144,6 +144,18 @@ export function createPaymentsCollection(pluginConfig: BillingPluginConfig): Col
       useAsTitle: 'id',
     },
     fields,
+    defaultPopulate: {
+      id: true,
+      provider: true,
+      status: true,
+      amount: true,
+      currency: true,
+      description: true,
+      checkoutUrl: true,
+      providerId: true,
+      metadata: true,
+      providerData: true,
+    },
     hooks: {
       afterChange: [
         async ({ doc, operation, req, previousDoc }) => {

src/plugin/index.ts

@@ -4,7 +4,7 @@ import type { Config, Payload } from 'payload'
 import { createSingleton } from './singleton'
 import type { PaymentProvider } from '../providers/index'
 
-const singleton = createSingleton(Symbol('billingPlugin'))
+const singleton = createSingleton(Symbol.for('@xtr-dev/payload-billing'))
 
 type BillingPlugin = {
   config: BillingPluginConfig

src/providers/mollie.ts

@@ -14,7 +14,7 @@ import {
 import { formatAmountForProvider, isValidAmount, isValidCurrencyCode } from './currency'
 import { createContextLogger } from '../utils/logger'
 
-const symbol = Symbol('mollie')
+const symbol = Symbol.for('@xtr-dev/payload-billing/mollie')
 export type MollieProviderConfig = Parameters<typeof createMollieClient>[0]
 
 /**

src/providers/stripe.ts

@@ -14,7 +14,7 @@ import {
 import { isValidAmount, isValidCurrencyCode } from './currency'
 import { createContextLogger } from '../utils/logger'
 
-const symbol = Symbol('stripe')
+const symbol = Symbol.for('@xtr-dev/payload-billing/stripe')
 
 export interface StripeProviderConfig {
   secretKey: string

src/providers/test.ts

@@ -6,7 +6,7 @@ import { handleWebhookError, logWebhookEvent } from './utils'
 import { isValidAmount, isValidCurrencyCode } from './currency'
 import { createContextLogger } from '../utils/logger'
 
-const TestModeWarningSymbol = Symbol('TestModeWarning')
+const TestModeWarningSymbol = Symbol.for('@xtr-dev/payload-billing/test-mode-warning')
 const hasGivenTestModeWarning = () => TestModeWarningSymbol in globalThis
 const setTestModeWarning = () => ((<any>globalThis)[TestModeWarningSymbol] = true)
 
@@ -492,7 +492,7 @@ export const testProvider = (testConfig: TestProviderConfig) => {
 
       // Set provider ID and data
       payment.providerId = testPaymentId
-      const paymentUrl = `${baseUrl}/api/payload-billing/test/payment/${testPaymentId}`
+      const paymentUrl = `${baseUrl}${uiRoute}/${testPaymentId}`
       const providerData: ProviderData = {
         raw: {
           id: testPaymentId,