commands: inform buyer when order is canceled

When the seller cancels an order, the buyer was getting a
confusing message:

```
You have cancelled the order ID: orderID
```

Now the bot sends a message that tells the buyer:

```
Order orderId has been cancelled. There is no need to create an invoice.
```

Fixes: #482

bot/commands.js

@@ -331,7 +331,7 @@ const cancelAddInvoice = async (ctx, order, job) => {
           );
         }
       } else {
-        await messages.successCancelOrderMessage(ctx, user, order, i18nCtx);
+        await messages.successCancelOrderInvoiceMessage(ctx, user, order, i18nCtx);
       }
       OrderEvents.orderUpdated(order);
     }

bot/messages.ts

@@ -966,6 +966,17 @@ const successCancelOrderMessage = async (ctx: MainContext, user: UserDocument, o
   }
 };
 
+const successCancelOrderInvoiceMessage = async (ctx: MainContext, user: UserDocument, order: IOrder, i18n: I18nContext) => {
+  try {
+    await ctx.telegram.sendMessage(
+      user.tg_id,
+      i18n.t('cancel_invoice', { orderId: order._id })
+    );
+  } catch (error) {
+    logger.error(error);
+  }
+};
+
 const counterPartyCancelOrderMessage = async (ctx: MainContext, user: UserDocument, order: IOrder, i18n: I18nContext) => {
   try {
     await ctx.telegram.sendMessage(
@@ -1667,6 +1678,7 @@ module.exports = {
   successCompleteOrderMessage,
   successCancelOrderByAdminMessage,
   successCancelOrderMessage,
+  successCancelOrderInvoiceMessage,
   badStatusOnCancelOrderMessage,
   orderIsAlreadyCanceledMessage,
   invoicePaymentFailedMessage,

locales/en.yaml

@@ -272,6 +272,7 @@ invoice_already_being_paid: You have alreday send an invoice for this order and
 lightning_address_saved: Lightning address has been saved
 cancel_error: This order cannot be cancelled at this moment
 cancel_success: 'You have cancelled the order ID: ${orderId}!'
+cancel_invoice: 'Order ${orderId} has been cancelled, no need to create an invoice.'
 cancelall_success: You have cancelled all your published orders!
 already_cancelled: The order has already been cancelled!
 order_cancelled_by_admin: 'Admin has cancelled the order ID: ${orderId}!'