feat: Whatsapp embedded signup (#11612)

## Description

This PR introduces WhatsApp Embedded Signup functionality, enabling
users to connect their WhatsApp Business accounts through Meta's
streamlined OAuth flow without manual webhook configuration. This
significantly improves the user experience by automating the entire
setup process.

**Key Features:**

- Embedded signup flow using Facebook SDK and Meta's OAuth 2.0
- Automatic webhook registration and phone number configuration
- Enhanced provider selection UI with card-based design
- Real-time progress tracking during signup process
- Comprehensive error handling and user feedback


## Required Configuration

The following environment variables must be configured by administrators
before this feature can be used:
Super Admin Configuration (via
super_admin/app_config?config=whatsapp_embedded)

- `WHATSAPP_APP_ID`: The Facebook App ID for WhatsApp Business API
integration
- `WHATSAPP_CONFIGURATION_ID`: The Configuration ID for WhatsApp
Embedded Signup flow (obtained from Meta Developer Portal)
- `WHATSAPP_APP_SECRET`: The App Secret for WhatsApp Embedded Signup
flow (required for token exchange)
![Screenshot 2025-06-09 at 11 21
08 AM](https://github.com/user-attachments/assets/1615fb0d-27fc-4d9e-b193-9be7894ea93a)


## How Has This Been Tested?

#### Backend Tests (RSpec):

- Authentication validation for embedded signup endpoints
- Authorization code validation and error handling
- Missing business parameter validation
- Proper response format for configuration endpoint
- Unauthorized access prevention

#### Manual Test Cases:

- Complete embedded signup flow (happy path)
- Provider selection UI navigation
- Facebook authentication popup handling
- Error scenarios (cancelled auth, invalid business data, API failures)
- Configuration presence/absence behavior

## Related Screenshots:

![Screenshot 2025-06-09 at 7 48
18 PM](https://github.com/user-attachments/assets/34001425-df11-4d78-9424-334461e3178f)
![Screenshot 2025-06-09 at 7 48
22 PM](https://github.com/user-attachments/assets/c09f4964-3aba-4c39-9285-d1e8e37d0e33)
![Screenshot 2025-06-09 at 7 48
32 PM](https://github.com/user-attachments/assets/a34d5382-7a91-4e1c-906e-dc2d570c864a)
![Screenshot 2025-06-09 at 10 43
05 AM](https://github.com/user-attachments/assets/a15840d8-8223-4513-82e4-b08f23c95927)
![Screenshot 2025-06-09 at 10 42
56 AM](https://github.com/user-attachments/assets/8c345022-38b5-44c4-aba2-0cda81389c69)


Fixes
https://linear.app/chatwoot/issue/CW-2131/spec-for-whatsapp-cloud-channels-sign-in-with-facebook

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>

spec/models/channel/whatsapp_spec.rb

@@ -61,4 +61,65 @@ RSpec.describe Channel::Whatsapp do
       expect(channel.provider_config['webhook_verify_token']).to eq '123'
     end
   end
+
+  describe 'webhook setup after creation' do
+    let(:account) { create(:account) }
+    let(:webhook_service) { instance_double(Whatsapp::WebhookSetupService) }
+
+    before do
+      allow(Whatsapp::WebhookSetupService).to receive(:new).and_return(webhook_service)
+      allow(webhook_service).to receive(:perform)
+    end
+
+    context 'when channel is created through embedded signup' do
+      it 'does not raise error if webhook setup fails' do
+        allow(webhook_service).to receive(:perform).and_raise(StandardError, 'Webhook error')
+
+        expect do
+          create(:channel_whatsapp,
+                 account: account,
+                 provider: 'whatsapp_cloud',
+                 provider_config: {
+                   'source' => 'embedded_signup',
+                   'business_account_id' => 'test_waba_id',
+                   'api_key' => 'test_access_token'
+                 },
+                 validate_provider_config: false,
+                 sync_templates: false)
+        end.not_to raise_error
+      end
+    end
+
+    context 'when channel is created through manual setup' do
+      it 'does not setup webhooks' do
+        expect(Whatsapp::WebhookSetupService).not_to receive(:new)
+
+        create(:channel_whatsapp,
+               account: account,
+               provider: 'whatsapp_cloud',
+               provider_config: {
+                 'business_account_id' => 'test_waba_id',
+                 'api_key' => 'test_access_token'
+               },
+               validate_provider_config: false,
+               sync_templates: false)
+      end
+    end
+
+    context 'when channel is created with different provider' do
+      it 'does not setup webhooks for 360dialog provider' do
+        expect(Whatsapp::WebhookSetupService).not_to receive(:new)
+
+        create(:channel_whatsapp,
+               account: account,
+               provider: 'default',
+               provider_config: {
+                 'source' => 'embedded_signup',
+                 'api_key' => 'test_360dialog_key'
+               },
+               validate_provider_config: false,
+               sync_templates: false)
+      end
+    end
+  end
 end