Add create voucher action and system test

app/controllers/admin/vouchers_controller.rb

@@ -2,10 +2,35 @@
 
 module Admin
   class VouchersController < ResourceController
+    before_action :load_enterprise
 
-   def new
-     @enterprise = Enterprise.find_by permalink: params[:enterprise_id]
-     @voucher = Voucher.new
-   end
+    def new
+      @voucher = Voucher.new
+    end
+
+    def create
+      voucher_params = permitted_resource_params.merge(enterprise: @enterprise)
+      @voucher = Voucher.create(voucher_params)
+
+      if @voucher.save
+        redirect_to(
+          "#{edit_admin_enterprise_path(@enterprise)}#vouchers_panel",
+          flash: { success: flash_message_for(@voucher, :successfully_created) }
+        )
+      else
+        flash[:error] = @voucher.errors.full_messages.to_sentence
+        render :new
+      end
+    end
+
+    private
+
+    def load_enterprise
+      @enterprise = Enterprise.find_by permalink: params[:enterprise_id]
+    end
+
+    def permitted_resource_params
+      params.require(:voucher).permit(:code)
+    end
   end
 end