fix: ENG-3901 Adds additional postcode validation (#437)

[ENG-3901]

On both RND 2025 and 2026 we found there's an inconsistency between the
regex used by our storybook's PostcodeLookup component, and the backend
of serverless-giftaid.

We found that the backend was stricter than storybook in its validation
of the outcode (the first half of a postcode) - the postcode `cro 7tp`
was being allowed by the frontend, but rejected by the backend.

The goal here is to make the FE & BE* are stick to the same regex rule.
*(the backend itself doesn't validate, it defers to a function in
data-models. So really we're matching that.)

There's a few tests updated and removed: ones that disallowed not having
a space, or not using capital letters. The backend/data-models
normalises what it's given, so postcodes like bn16aa will get
transformed into BN1 6AA.

To test it works, we should NOT be able to use the above postcode in
either form (the main page, or the /update page)

Last point: I did this a year ago when I had an IDE rule that strips
whitespace. While I don't have that rule enabled anymore, I do still
want to keep the many whitespace removal changes here. A noisier diff,
but it is correct as that is errant whitespace and it shouldn't be here.
I will die on this hill

[ENG-3901]:
https://comicrelief.atlassian.net/browse/ENG-3901?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

---------

Co-authored-by: Krupa Pammi <k.pammi@comicrelief.com>

Author: curlyfriesplease

playwright-local/tests/submit/addressValidation.spec.js

@@ -5,29 +5,31 @@ test.describe('Address validation', () => {
 
   test.beforeEach(async ({ page }) => {
     await page.goto('/', { timeout: 30000 });
-  
+
     await page.waitForLoadState('domcontentloaded');
     await page.locator('#field-label--giftaid').click();
     await page.locator('#field-input--mobile').fill('07123456789');
     await page.locator('input#field-input--firstname').fill('test');
     await page.locator('input#field-input--lastname').fill('user');
   });
-  
+
   test('empty postcode should show error message', async ({ page }) => {
     await page.locator('input#field-input--postcode').fill('');
     await page.locator('button[type=submit]').click();
     await expect(page.locator('div#field-error--postcode > span')).toHaveText('Please enter your postcode');
     await page.close();
   });
-  
+
   test('invalid postcodes should show error messages', async ({ page }) => {
     await page.locator('input#field-input--postcode').fill('12SE17TP');
     await expect(page.locator('div#field-error--postcode > span')).toHaveText('Please enter a valid UK postcode, using a space. For non-UK addresses, please use manual entry below.');
     await page.locator('input#field-input--postcode').fill('comic relief');
     await expect(page.locator('div#field-error--postcode > span')).toHaveText('Please enter a valid UK postcode, using a space. For non-UK addresses, please use manual entry below.');
+    await page.locator('input#field-input--postcode').fill('cro 7tp');
+    await expect(page.locator('div#field-error--postcode > span')).toHaveText('Please enter a valid UK postcode, using a space. For non-UK addresses, please use manual entry below.');
     await page.close();
   });
-  
+
   test('enter postcode but submit without selecting address should show error message', async ({ page }) => {
     await page.locator('input#field-input--postcode').fill('SE1 7TP');
     await page.locator('#postcode_button').click();
@@ -36,7 +38,7 @@ test.describe('Address validation', () => {
     await expect(page.locator('div#field-error--addressSelect > span')).toHaveText('Please select your address');
     await page.close();
   });
-  
+
   test('clicking on manual address link should show address fields', async ({ page }) => {
     await page.locator('input#field-input--postcode').fill('SE1 7TP');
     await expect(page.locator('a[aria-describedby=field-error--addressDetails]')).toBeVisible();
@@ -48,17 +50,17 @@ test.describe('Address validation', () => {
     await expect(page.locator('select#field-select--country')).toBeVisible();
     await page.close();
   });
-  
+
   test('validate address fields', async ({ page }) => {
     await page.locator('input#field-input--postcode').fill('SE1 7TP');
     await page.locator('a[aria-describedby=field-error--addressDetails]').click();
-    
+
     // Should see error message for address1 when inout with special characters is entered
     await page.locator('#field-input--address1').fill('@£%3dComic Relief');
     await expect(page.locator('#field-error--address1 > span')).toHaveText("This field only accepts alphanumeric characters and ' . - & _ /");
     await page.locator('#field-input--town').fill('  Comic Relief');
     await expect(page.locator('#field-error--town > span')).toHaveText("This field only accepts alphanumeric characters and ' . - & _ /");
-    
+
     await page.close();
   });
 });

playwright-local/tests/submit/postcodeLookup.spec.js

@@ -16,8 +16,6 @@ test.describe('Postcode validation', () => {
   test('Postcode formatting errors', async ({ page }) => {
     const postcodes = [
       { code: 'S E 1 7 T P', message: 'Please enter a valid UK postcode, using a space. For non-UK addresses, please use manual entry below.' },
-      { code: 'se17tp', message: 'Please enter a valid UK postcode, using a space. For non-UK addresses, please use manual entry below.' },
-      { code: 'SE17TP', message: 'Please enter a valid UK postcode, using a space. For non-UK addresses, please use manual entry below.' },
       { code: 'SE$%TP', message: 'Please enter a valid UK postcode, using a space. For non-UK addresses, please use manual entry below.' }
     ];