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>

app/models/channel/whatsapp.rb

@@ -33,6 +33,7 @@ class Channel::Whatsapp < ApplicationRecord
   validate :validate_provider_config
 
   after_create :sync_templates
+  after_create_commit :setup_webhooks
 
   def name
     'Whatsapp'
@@ -67,4 +68,41 @@ class Channel::Whatsapp < ApplicationRecord
   def validate_provider_config
     errors.add(:provider_config, 'Invalid Credentials') unless provider_service.validate_provider_config?
   end
+
+  def setup_webhooks
+    return unless should_setup_webhooks?
+
+    perform_webhook_setup
+  rescue StandardError => e
+    handle_webhook_setup_error(e)
+  end
+
+  def should_setup_webhooks?
+    whatsapp_cloud_provider? && embedded_signup_source? && webhook_config_present?
+  end
+
+  def whatsapp_cloud_provider?
+    provider == 'whatsapp_cloud'
+  end
+
+  def embedded_signup_source?
+    provider_config['source'] == 'embedded_signup'
+  end
+
+  def webhook_config_present?
+    provider_config['business_account_id'].present? && provider_config['api_key'].present?
+  end
+
+  def perform_webhook_setup
+    business_account_id = provider_config['business_account_id']
+    api_key = provider_config['api_key']
+
+    Whatsapp::WebhookSetupService.new(self, business_account_id, api_key).perform
+  end
+
+  def handle_webhook_setup_error(error)
+    Rails.logger.error "[WHATSAPP] Webhook setup failed: #{error.message}"
+    # Don't raise the error to prevent channel creation from failing
+    # Webhooks can be retried later
+  end
 end