feat: Replace alertMixin usage with useAlert (#9793)

# Pull Request Template

## Description

This PR will replace the usage of `alertMixin` from the code base with
the `useAlert` composable.

Fixes
https://linear.app/chatwoot/issue/CW-3462/replace-alertmixin-usage-with-usealert

## Type of change

- [x] Breaking change (fix or feature that would cause existing
functionality not to work as expected)

## How Has This Been Tested?

Please refer this issue description

https://linear.app/chatwoot/issue/CW-3462/replace-alertmixin-usage-with-usealert


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] 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

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

app/javascript/v3/views/login/Index.vue

@@ -91,6 +91,7 @@
 </template>
 
 <script>
+import { useAlert } from 'dashboard/composables';
 import { required, email } from 'vuelidate/lib/validators';
 import globalConfigMixin from 'shared/mixins/globalConfigMixin';
 import SubmitButton from '../../components/Button/SubmitButton.vue';
@@ -104,7 +105,6 @@ const ERROR_MESSAGES = {
   'no-account-found': 'LOGIN.OAUTH.NO_ACCOUNT_FOUND',
   'business-account-only': 'LOGIN.OAUTH.BUSINESS_ACCOUNTS_ONLY',
 };
-import alertMixin from 'shared/mixins/alertMixin';
 
 export default {
   components: {
@@ -113,7 +113,7 @@ export default {
     Spinner,
     SubmitButton,
   },
-  mixins: [globalConfigMixin, alertMixin],
+  mixins: [globalConfigMixin],
   props: {
     ssoAuthToken: { type: String, default: '' },
     ssoAccountId: { type: String, default: '' },
@@ -164,7 +164,7 @@ export default {
     }
     if (this.authError) {
       const message = ERROR_MESSAGES[this.authError] ?? 'LOGIN.API.UNAUTH';
-      this.showAlert(this.$t(message));
+      useAlert(this.$t(message));
       // wait for idle state
       this.requestIdleCallbackPolyfill(() => {
         // Remove the error query param from the url
@@ -191,7 +191,7 @@ export default {
       // Reset loading, current selected agent
       this.loginApi.showLoading = false;
       this.loginApi.message = message;
-      this.showAlert(this.loginApi.message);
+      useAlert(this.loginApi.message);
     },
     submitLogin() {
       if (this.$v.credentials.email.$invalid && !this.email) {