feat: show email subject in conversation search results (#10843)

# Pull Request Template

## Description

This addresses #10842. It exposes `additional_attributes` in the
conversations search endpoint, uses it in
`SearchResultConversationsList` to pass
`conversation.additional_attributes?.mail_subject` down to
`SearchResultConversationItem`, which in turn displays it.

Fixes #10842

## Type of change

Please delete options that are not relevant.

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality not to work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

I have tested this locally by searching for conversations. See this
screenshot where I searched for "noreply":
![Screenshot from 2025-02-05
11-04-54](https://github.com/user-attachments/assets/689e3e99-c20b-48a7-9c3e-35d45ffeafc1)

I would love to add automated tests but I’m not sure how to do that.

## 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
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

app/javascript/dashboard/modules/search/components/SearchResultConversationsList.vue

@@ -1,9 +1,10 @@
 <script setup>
+import { defineProps, computed } from 'vue';
 import { useMapGetter } from 'dashboard/composables/store.js';
 import SearchResultSection from './SearchResultSection.vue';
 import SearchResultConversationItem from './SearchResultConversationItem.vue';
 
-defineProps({
+const props = defineProps({
   conversations: {
     type: Array,
     default: () => [],
@@ -23,6 +24,13 @@ defineProps({
 });
 
 const accountId = useMapGetter('getCurrentAccountId');
+
+const conversationsWithSubject = computed(() => {
+  return props.conversations.map(conversation => ({
+    ...conversation,
+    mail_subject: conversation.additional_attributes?.mail_subject || '',
+  }));
+});
 </script>
 
 <template>
@@ -34,7 +42,10 @@ const accountId = useMapGetter('getCurrentAccountId');
     :is-fetching="isFetching"
   >
     <ul v-if="conversations.length" class="space-y-1.5 list-none">
-      <li v-for="conversation in conversations" :key="conversation.id">
+      <li
+        v-for="conversation in conversationsWithSubject"
+        :key="conversation.id"
+      >
         <SearchResultConversationItem
           :id="conversation.id"
           :name="conversation.contact.name"
@@ -42,6 +53,7 @@ const accountId = useMapGetter('getCurrentAccountId');
           :account-id="accountId"
           :inbox="conversation.inbox"
           :created-at="conversation.created_at"
+          :email-subject="conversation.mail_subject"
         />
       </li>
     </ul>