feat(ee): Setup advanced, performant message search (#12193)

We now support searching within the actual message content, email
subject lines, and audio transcriptions. This enables a faster, more
accurate search experience going forward. Unlike the standard message
search, which is limited to the last 3 months, this search has no time
restrictions.

The search engine also accounts for small variations in queries. Minor
spelling mistakes, such as searching for slck instead of Slack, will
still return the correct results. It also ignores differences in accents
and diacritics, so searching for Deja vu will match content containing
Déjà vu.


We can also refine searches in the future by criteria such as:
- Searching within a specific inbox
- Filtering by sender or recipient
- Limiting to messages sent by an agent


Fixes https://github.com/chatwoot/chatwoot/issues/11656
Fixes https://github.com/chatwoot/chatwoot/issues/10669
Fixes https://github.com/chatwoot/chatwoot/issues/5910



---

Rake tasks to reindex all the messages. 

```sh
bundle exec rake search:all
```

Rake task to reindex messages from one account only
```sh
bundle exec rake search:account ACCOUNT_ID=1
```

spec/models/message_spec.rb

@@ -613,4 +613,57 @@ RSpec.describe Message do
       end
     end
   end
+
+  describe '#should_index?' do
+    let(:account) { create(:account) }
+    let(:conversation) { create(:conversation, account: account) }
+    let(:message) { create(:message, conversation: conversation, account: account) }
+
+    before do
+      allow(ChatwootApp).to receive(:advanced_search_allowed?).and_return(true)
+      account.enable_features('advanced_search')
+    end
+
+    context 'when advanced search is not allowed globally' do
+      before do
+        allow(ChatwootApp).to receive(:advanced_search_allowed?).and_return(false)
+      end
+
+      it 'returns false' do
+        expect(message.should_index?).to be false
+      end
+    end
+
+    context 'when advanced search feature is not enabled for account' do
+      before do
+        account.disable_features('advanced_search')
+      end
+
+      it 'returns false' do
+        expect(message.should_index?).to be false
+      end
+    end
+
+    context 'when message type is not incoming or outgoing' do
+      before do
+        message.message_type = 'activity'
+      end
+
+      it 'returns false' do
+        expect(message.should_index?).to be false
+      end
+    end
+
+    context 'when all conditions are met' do
+      it 'returns true for incoming message' do
+        message.message_type = 'incoming'
+        expect(message.should_index?).to be true
+      end
+
+      it 'returns true for outgoing message' do
+        message.message_type = 'outgoing'
+        expect(message.should_index?).to be true
+      end
+    end
+  end
 end