fix: only subscribe calls webhook field when voice calling enabled (#14718)

## Description

Solves issue https://github.com/chatwoot/chatwoot/issues/14690

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)

## How has this been tested?

- UI flows

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] 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

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/models/channel/whatsapp.rb

@@ -69,8 +69,10 @@ class Channel::Whatsapp < ApplicationRecord
     end
   end
 
-  # Enables voice: turns calling on at Meta (idempotent), subscribes the `calls`
-  # webhook field, and sets calling_enabled. Raises on Meta failure.
+  # Enables voice: turns calling on at Meta (idempotent), then re-registers webhooks
+  # with the in-memory calling_enabled flag so the `calls` field is subscribed. The
+  # flag is persisted only after registration succeeds, so a webhook failure can't
+  # leave the inbox reporting voice_enabled? while the WABA isn't subscribed to calls.
   # Saved with validate: false to skip validate_provider_config's remote credential
   # re-check, which could spuriously fail and desync the flag from Meta.
   def enable_voice_calling!
@@ -78,21 +80,21 @@ class Channel::Whatsapp < ApplicationRecord
     raise 'WhatsApp calling requires the channel_voice feature' unless account.feature_enabled?('channel_voice')
 
     provider_service.update_calling_status('ENABLED')
-    webhook_setup_service.register_callback
     self.provider_config = provider_config.merge('calling_enabled' => true)
+    webhook_setup_service.register_callback
     save!(validate: false)
   end
 
-  # Disables voice: unsets calling_enabled (gates the call subsystem) and drops
-  # `calls` from the webhook subscription (best-effort, so a Meta outage can't
-  # trap admins). Leaves Meta's WABA calling.status untouched.
+  # Disables voice: unsets calling_enabled (gates the call subsystem) and re-registers
+  # webhooks, which drops `calls` from the subscription (best-effort, so a Meta outage
+  # can't trap admins). Leaves Meta's WABA calling.status untouched.
   def disable_voice_calling!
     raise 'WhatsApp calling requires a whatsapp_cloud inbox' unless voice_calling_supported?
 
     self.provider_config = provider_config.merge('calling_enabled' => false)
     save!(validate: false)
     begin
-      webhook_setup_service.register_callback(subscribed_fields: %w[messages smb_message_echoes])
+      webhook_setup_service.register_callback
     rescue StandardError => e
       Rails.logger.warn "[WHATSAPP CALL] disable webhook re-subscribe failed: #{e.message}"
     end

app/services/whatsapp/facebook_api_client.rb

@@ -60,7 +60,7 @@ class Whatsapp::FacebookApiClient
     data['code_verification_status'] == 'VERIFIED'
   end
 
-  WEBHOOK_DEFAULT_FIELDS = %w[messages smb_message_echoes calls].freeze
+  WEBHOOK_DEFAULT_FIELDS = %w[messages smb_message_echoes].freeze
 
   def subscribe_waba_webhook(waba_id, callback_url, verify_token, subscribed_fields: WEBHOOK_DEFAULT_FIELDS)
     # Step 1: Subscribe app to WABA first (required before override)

app/services/whatsapp/webhook_setup_service.rb

@@ -17,9 +17,9 @@ class Whatsapp::WebhookSetupService
     setup_webhook
   end
 
-  def register_callback(subscribed_fields: nil)
+  def register_callback
     validate_parameters!
-    setup_webhook(subscribed_fields: subscribed_fields)
+    setup_webhook
   end
 
   private
@@ -55,21 +55,23 @@ class Whatsapp::WebhookSetupService
     @channel.save!
   end
 
-  def setup_webhook(subscribed_fields: nil)
+  def setup_webhook
     callback_url = build_callback_url
     verify_token = @channel.provider_config['webhook_verify_token']
 
-    args = [@waba_id, callback_url, verify_token]
-    if subscribed_fields
-      @api_client.subscribe_waba_webhook(*args, subscribed_fields: subscribed_fields)
-    else
-      @api_client.subscribe_waba_webhook(*args)
-    end
+    @api_client.subscribe_waba_webhook(@waba_id, callback_url, verify_token, subscribed_fields: subscribed_fields)
   rescue StandardError => e
     Rails.logger.error("[WHATSAPP] Webhook setup failed: #{e.message}")
     raise "Webhook setup failed: #{e.message}"
   end
 
+  # Subscribe to `calls` only when voice calling is enabled on the inbox
+  def subscribed_fields
+    fields = %w[messages smb_message_echoes]
+    fields << 'calls' if @channel.provider_config['calling_enabled']
+    fields
+  end
+
   def build_callback_url
     frontend_url = ENV.fetch('FRONTEND_URL', nil)
     phone_number = @channel.phone_number