[PUI] Form error fix (#8204)

* Handle simple string error message

* Add playwright test for form validation

* Render stock unit price / total value

* Fix for TextField:

- Prevent unnecessary value change
- This was removing the field error

* Add playwright test for supplier form validation

src/frontend/tests/pui_basic.spec.ts

@@ -2,7 +2,7 @@ import { expect, test } from './baseFixtures.js';
 import { baseUrl, user } from './defaults.js';
 import { doLogin, doQuickLogin } from './login.js';
 
-test('PUI - Basic Login Test', async ({ page }) => {
+test('Basic Login Test', async ({ page }) => {
   await doLogin(page);
 
   // Check that the username is provided
@@ -35,7 +35,7 @@ test('PUI - Basic Login Test', async ({ page }) => {
   await page.getByLabel('username');
 });
 
-test('PUI - Quick Login Test', async ({ page }) => {
+test('Quick Login Test', async ({ page }) => {
   await doQuickLogin(page);
 
   // Check that the username is provided