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/dashboard/components/layout/sidebarComponents/AddAccountModal.vue

@@ -51,10 +51,9 @@
 <script>
 import { required, minLength } from 'vuelidate/lib/validators';
 import { mapGetters } from 'vuex';
-import alertMixin from 'shared/mixins/alertMixin';
+import { useAlert } from 'dashboard/composables';
 
 export default {
-  mixins: [alertMixin],
   props: {
     show: {
       type: Boolean,
@@ -88,13 +87,13 @@ export default {
           account_name: this.accountName,
         });
         this.$emit('close-account-create-modal');
-        this.showAlert(this.$t('CREATE_ACCOUNT.API.SUCCESS_MESSAGE'));
+        useAlert(this.$t('CREATE_ACCOUNT.API.SUCCESS_MESSAGE'));
         window.location = `/app/accounts/${account_id}/dashboard`;
       } catch (error) {
         if (error.response.status === 422) {
-          this.showAlert(this.$t('CREATE_ACCOUNT.API.EXIST_MESSAGE'));
+          useAlert(this.$t('CREATE_ACCOUNT.API.EXIST_MESSAGE'));
         } else {
-          this.showAlert(this.$t('CREATE_ACCOUNT.API.ERROR_MESSAGE'));
+          useAlert(this.$t('CREATE_ACCOUNT.API.ERROR_MESSAGE'));
         }
       }
     },