chore: Introduce enterprise edition license (#3209)

- Initialize an "enterprise" folder that is copyrighted.
- You can remove this folder and the system will continue functioning normally, in case you want a purely MIT licensed product.
- Enable limit on the number of user accounts in enterprise code.
- Use enterprise edition injector methods (inspired from Gitlab).
- SaaS software would run enterprise edition software always.

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/controllers/concerns/request_exception_handler.rb

@@ -31,6 +31,10 @@ module RequestExceptionHandler
     render json: { error: message }, status: :unprocessable_entity
   end
 
+  def render_payment_required(message)
+    render json: { error: message }, status: :payment_required
+  end
+
   def render_internal_server_error(message)
     render json: { error: message }, status: :internal_server_error
   end