fix: Optimize Message search_data to prevent OpenSearch field explosion (#12786)

## Description

Refactored the `Message#search_data` method to prevent exceeding
OpenSearch's 1000 field limit during reindex operations.

**Problem:** The previous implementation serialized entire ActiveRecord
objects (Inbox, Sender, Conversation) with all their JSONB fields,
causing dynamic field explosion in OpenSearch. This resulted in
`Searchkick::ImportError` with "Limit of total fields [1000] has been
exceeded".

**Solution:** Whitelisted only necessary fields for search and
filtering, and flattened JSONB `custom_attributes` into key-value pair
arrays to prevent unbounded field creation.

Linked to: CW-5861

## Type of change

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

## How Has This Been Tested?

- Verified rubocop passes with no offenses
- Code review of search field usage from
`enterprise/app/services/enterprise/search_service.rb`
- Analyzed actual search queries to determine required indexed fields

**Still needed:**
- Full reindex test on staging/production environment
- Verify search functionality still works after reindex
- Confirm field count is under 1000 limit

## Changes Made

### Before
- Indexed 1000+ fields (entire AR objects with JSONB)
- `inbox` = full Inbox object (23+ fields + JSONB)
- `sender` = full Contact/User/AgentBot object (10+ fields + JSONB)
- `conversation` = full push_event_data
- Dynamic JSONB keys creating unlimited fields

### After
- ~35-40 controlled fields
- Whitelisted search fields: `content`, `attachment_transcribed_text`,
`email_subject`
- Filter fields: `account_id`, `inbox_id`, `conversation_id`,
`sender_id`, `sender_type`, etc.
- Flattened `custom_attributes`: `[{key, value, value_type}]` format
- Helper methods: `search_conversation_data`, `search_inbox_data`,
`search_sender_data`, `search_additional_data`

## 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
- [ ] Any dependent changes have been merged and published in downstream
modules

## Post-merge Steps

After merging, the following steps are required:

1. **Reindex all messages:**
   ```bash
   bundle exec rails runner "Message.reindex"
   ```

2. **Verify field count:**
   ```bash
   bundle exec rails runner "
     client = Searchkick.client
     index_name = Message.searchkick_index.name
     mapping = client.indices.get_mapping(index: index_name)
     fields = mapping.dig(index_name, 'mappings', 'properties')
     puts 'Total fields: ' + fields.keys.count.to_s
   "
   ```

3. **Test search functionality** to ensure queries still work as
expected

---------

Co-authored-by: Vishnu Narayanan <iamwishnu@gmail.com>
Co-authored-by: Pranav <pranav@chatwoot.com>

app/models/message.rb

@@ -153,15 +153,6 @@ class Message < ApplicationRecord
     merge_sender_attributes(data)
   end
 
-  def search_data
-    data = attributes.symbolize_keys
-    data[:conversation] = conversation.present? ? conversation_push_event_data : nil
-    data[:attachments] = attachments.map(&:push_event_data) if attachments.present?
-    data[:sender] = sender.push_event_data if sender
-    data[:inbox] = inbox
-    data
-  end
-
   def conversation_push_event_data
     {
       assignee_id: conversation.assignee_id,
@@ -259,6 +250,10 @@ class Message < ApplicationRecord
     true
   end
 
+  def search_data
+    Messages::SearchDataPresenter.new(self).search_data
+  end
+
   private
 
   def prevent_message_flooding

app/presenters/messages/search_data_presenter.rb

@@ -0,0 +1,58 @@
+class Messages::SearchDataPresenter < SimpleDelegator
+  def search_data
+    {
+      **searchable_content,
+      **message_attributes,
+      **search_additional_data,
+      conversation: conversation_data
+    }
+  end
+
+  private
+
+  def searchable_content
+    {
+      content: content,
+      attachments: attachment_data,
+      content_attributes: content_attributes_data
+    }
+  end
+
+  def message_attributes
+    {
+      account_id: account_id,
+      inbox_id: inbox_id,
+      conversation_id: conversation_id,
+      message_type: message_type,
+      private: private,
+      created_at: created_at,
+      source_id: source_id,
+      sender_id: sender_id,
+      sender_type: sender_type
+    }
+  end
+
+  def attachment_data
+    attachments.filter_map do |a|
+      { transcribed_text: a.meta&.dig('transcribed_text') }
+    end.presence
+  end
+
+  def content_attributes_data
+    email_subject = content_attributes.dig(:email, :subject)
+    return {} if email_subject.blank?
+
+    { email: { subject: email_subject } }
+  end
+
+  def conversation_data
+    { id: conversation.display_id }
+  end
+
+  def search_additional_data
+    {
+      campaign_id: additional_attributes&.dig('campaign_id'),
+      automation_rule_id: content_attributes&.dig('automation_rule_id')
+    }
+  end
+end

spec/presenters/messages/search_data_presenter_spec.rb

@@ -0,0 +1,78 @@
+require 'rails_helper'
+
+RSpec.describe Messages::SearchDataPresenter do
+  let(:presenter) { described_class.new(message) }
+  let(:account) { create(:account) }
+  let(:inbox) { create(:inbox, account: account) }
+  let(:contact) { create(:contact, account: account) }
+  let(:conversation) { create(:conversation, account: account, inbox: inbox, contact: contact) }
+  let(:message) { create(:message, account: account, inbox: inbox, conversation: conversation, sender: contact) }
+
+  describe '#search_data' do
+    let(:expected_data) do
+      {
+        content: message.content,
+        account_id: message.account_id,
+        inbox_id: message.inbox_id,
+        conversation_id: message.conversation_id,
+        message_type: message.message_type,
+        private: message.private,
+        created_at: message.created_at,
+        source_id: message.source_id,
+        sender_id: message.sender_id,
+        sender_type: message.sender_type,
+        conversation: {
+          id: conversation.display_id
+        }
+      }
+    end
+
+    it 'returns search index payload with core fields' do
+      expect(presenter.search_data).to include(expected_data)
+    end
+
+    context 'with attachments' do
+      before do
+        attachment = message.attachments.new(account_id: message.account_id, file_type: :image)
+        attachment.file.attach(io: Rails.root.join('spec/assets/avatar.png').open, filename: 'avatar.png', content_type: 'image/png')
+        attachment.meta = { 'transcribed_text' => 'Hello world' }
+      end
+
+      it 'includes attachment transcriptions' do
+        attachments_data = presenter.search_data[:attachments]
+        expect(attachments_data).to be_an(Array)
+        expect(attachments_data.first).to include(transcribed_text: 'Hello world')
+      end
+    end
+
+    context 'with email content attributes' do
+      before do
+        message.update(
+          content_attributes: { email: { subject: 'Test Subject' } }
+        )
+      end
+
+      it 'includes email subject' do
+        content_attrs = presenter.search_data[:content_attributes]
+        expect(content_attrs[:email][:subject]).to eq('Test Subject')
+      end
+    end
+
+    context 'with campaign and automation data' do
+      before do
+        message.update(
+          additional_attributes: { 'campaign_id' => '123' },
+          content_attributes: { 'automation_rule_id' => '456' }
+        )
+      end
+
+      it 'includes campaign_id' do
+        expect(presenter.search_data[:campaign_id]).to eq('123')
+      end
+
+      it 'includes automation_rule_id' do
+        expect(presenter.search_data[:automation_rule_id]).to eq('456')
+      end
+    end
+  end
+end