feat: Rewrite customAttributeMixin to validation helper (#9916)

# Pull Request Template

## Description

This PR will replace the use of `customAttributeMixin` with
`shared/helpers/Validators` helper.

Fixes
https://linear.app/chatwoot/issue/CW-3446/rewrite-customattributemixin-mixin-to-a-composable

**Files updated**
1. widget/components/PreChat/Form.vue
2. dashboard/components/CustomAttribute.vue
3. dashboard/routes/dashboard/settings/attributes/EditAttribute.vue

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

Test the custom validation is working or not with the custom attributes.


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

app/javascript/shared/helpers/specs/ValidatorsHelper.spec.js

@@ -8,6 +8,7 @@ import {
   isPhoneNumberValid,
   isNumber,
   isDomain,
+  getRegexp,
 } from '../Validators';
 
 describe('#shouldBeUrl', () => {
@@ -115,3 +116,40 @@ describe('#startsWithPlus', () => {
     expect(startsWithPlus('123456789')).toEqual(false);
   });
 });
+
+describe('#getRegexp', () => {
+  it('should create a correct RegExp object', () => {
+    const regexPattern = '/^[a-z]+$/i';
+    const regex = getRegexp(regexPattern);
+
+    expect(regex).toBeInstanceOf(RegExp);
+    expect(regex.toString()).toBe(regexPattern);
+
+    expect(regex.test('abc')).toBe(true);
+    expect(regex.test('ABC')).toBe(true);
+    expect(regex.test('123')).toBe(false);
+  });
+
+  it('should handle regex with flags', () => {
+    const regexPattern = '/hello/gi';
+    const regex = getRegexp(regexPattern);
+
+    expect(regex).toBeInstanceOf(RegExp);
+    expect(regex.toString()).toBe(regexPattern);
+
+    expect(regex.test('hello')).toBe(true);
+    expect(regex.test('HELLO')).toBe(false);
+    expect(regex.test('Hello World')).toBe(true);
+  });
+
+  it('should handle regex with special characters', () => {
+    const regexPattern = '/\\d{3}-\\d{2}-\\d{4}/';
+    const regex = getRegexp(regexPattern);
+
+    expect(regex).toBeInstanceOf(RegExp);
+    expect(regex.toString()).toBe(regexPattern);
+
+    expect(regex.test('123-45-6789')).toBe(true);
+    expect(regex.test('12-34-5678')).toBe(false);
+  });
+});