display time since unregistered token was read

imaginaerraum_door_admin/templates/register.html

@@ -34,7 +34,7 @@
       <h4 class="alert-heading">Unregistrierter Token gelesen:</h4>
       <p>Token ID: {{ token['token'] }}</p>
       <hr>
-      <p class="mb-0">Zeitstempel (UTC): {{ token['timestamp']}}</p>
+      <p class="mb-0">Zeitstempel (UTC): {{ token['timestamp']}} (vor {{ token['timedelta_minutes'] }} Minuten)</p>
     </div>
 
     <div class="p-2 bg-light border">

imaginaerraum_door_admin/webapp.py

@@ -507,8 +507,10 @@ def create_application(config):
 
         recent_token = {}
         if {'token', 'timestamp'}.issubset(set(token.keys())):
-            if token['timestamp'] >= datetime.now() - timedelta(minutes=10):
+            dt = datetime.utcnow() - token['timestamp']
+            if  dt < timedelta(minutes=10):
                 recent_token = token
+                recent_token['timedelta_minutes'] = int(dt.total_seconds() / 60.0)
 
         form = TokenForm()
         if request.method == 'GET':