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/javascript/dashboard/i18n/locale/en/inboxMgmt.json

@@ -222,10 +222,17 @@
         "DESC": "Start supporting your customers via WhatsApp.",
         "PROVIDERS": {
           "LABEL": "API Provider",
+          "WHATSAPP_EMBEDDED": "WhatsApp Business",
           "TWILIO": "Twilio",
           "WHATSAPP_CLOUD": "WhatsApp Cloud",
+          "WHATSAPP_CLOUD_DESC": "Quick setup through Meta",
+          "TWILIO_DESC": "Connect via Twilio credentials",
           "360_DIALOG": "360Dialog"
         },
+        "SELECT_PROVIDER": {
+          "TITLE": "Select your API provider",
+          "DESCRIPTION": "Choose your WhatsApp provider. You can connect directly through Meta which requires no setup, or connect through Twilio using your account credentials."
+        },
         "INBOX_NAME": {
           "LABEL": "Inbox Name",
           "PLACEHOLDER": "Please enter an inbox name",
@@ -264,6 +271,28 @@
           "WEBHOOK_VERIFICATION_TOKEN": "Webhook Verification Token"
         },
         "SUBMIT_BUTTON": "Create WhatsApp Channel",
+        "EMBEDDED_SIGNUP": {
+          "TITLE": "Quick Setup with Meta",
+          "DESC": "You will be redirected to Meta to log into your WhatsApp Business account. Having admin access will help make the setup smooth and easy.",
+          "BENEFITS": {
+            "TITLE": "Benefits of Embedded Signup:",
+            "EASY_SETUP": "No manual configuration required",
+            "SECURE_AUTH": "Secure OAuth based authentication",
+            "AUTO_CONFIG": "Automatic webhook and phone number configuration"
+          },
+          "SUBMIT_BUTTON": "Connect with WhatsApp Business",
+          "AUTH_PROCESSING": "Authenticating with Meta",
+          "WAITING_FOR_BUSINESS_INFO": "Please complete business setup in the Meta window...",
+          "PROCESSING": "Setting up your WhatsApp Business Account",
+          "LOADING_SDK": "Loading Facebook SDK...",
+          "CANCELLED": "WhatsApp Signup was cancelled",
+          "SUCCESS_TITLE": "WhatsApp Business Account Connected!",
+          "WAITING_FOR_AUTH": "Waiting for authentication...",
+          "INVALID_BUSINESS_DATA": "Invalid business data received from Facebook. Please try again.",
+          "SIGNUP_ERROR": "Signup error occurred",
+          "AUTH_NOT_COMPLETED": "Authentication not completed. Please restart the process.",
+          "SUCCESS_FALLBACK": "WhatsApp Business Account has been successfully configured"
+        },
         "API": {
           "ERROR_MESSAGE": "We were not able to save the WhatsApp channel"
         }