Chore: Added tests for subscriptions_controller (#483)

Added tests for subscriptions_controller
ref: #37

app/controllers/application_controller.rb

@@ -67,7 +67,7 @@ class ApplicationController < ActionController::Base
   def check_subscription
     # This block is left over from the initial version of chatwoot
     # We might reuse this later in the hosted version of chatwoot.
-    return unless ENV['BILLING_ENABLED']
+    return if !ENV['BILLING_ENABLED'] || !current_user
 
     if current_subscription.trial? && current_subscription.expiry < Date.current
       render json: { error: 'Trial Expired' }, status: :trial_expired