show coupon expires date when user buys a coupon

app/dashboard/views/coupon.py

@@ -121,4 +121,7 @@ def coupon_route():
         PADDLE_VENDOR_ID=PADDLE_VENDOR_ID,
         PADDLE_COUPON_ID=PADDLE_COUPON_ID,
         can_use_coupon=can_use_coupon,
+        # a coupon is only valid until this date
+        # this is to avoid using the coupon to renew an account forever
+        max_coupon_date=arrow.now().shift(years=1, days=-1),
     )

templates/dashboard/coupon.html

@@ -52,6 +52,9 @@
         Can be an idea for a gift card :).
         After the payment, the coupon will be sent to you by email.
       </div>
+      <div class="alert alert-info">
+        The coupon must be used before {{ max_coupon_date.date().isoformat() }}
+      </div>
       <a href="#!" class="paddle_button btn btn-primary" data-product="{{ PADDLE_COUPON_ID }}">Buy 1-year SimpleLogin
         coupon</a>
     </div>