feat: split nights off an accommodation booking as separate periods

addresses #869f6z36v

templates/pdf/accommodation_booking.html.twig

@@ -83,6 +83,9 @@
                     <tr><th>Anreise</th><td>{{ booking.dateFrom|date('d.m.Y') }}</td></tr>
                     <tr><th>Abreise</th><td>{{ booking.dateTo|date('d.m.Y') }}</td></tr>
                     <tr><th>Nächte</th><td>{{ booking.nights }}</td></tr>
+                    {% if booking.periods is not empty %}
+                        <tr><th>Zeitraum Gruppe</th><td>{{ booking.mainDateFrom|date('d.m.Y') }} – {{ booking.mainDateTo|date('d.m.Y') }}</td></tr>
+                    {% endif %}
                     <tr><th>Anzahl Personen</th><td>{{ booking.paxCount }}</td></tr>
                     {% if booking.minorsCount > 0 %}
                         <tr><th>davon Kinder (0–3 J.)</th><td>{{ booking.minorsCount }}</td></tr>