feat: consistent display of included services and prices

src/Form/Service/ParticipantFieldOptionsProvider.php

@@ -605,10 +605,14 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
             return '';
         }
 
-        if (null === $service->price || 0.0 === $service->price) {
+        if (null === $service->price) {
             return $service->label;
         }
 
+        if (0.0 === $service->price) {
+            return sprintf('%s (inkl.)', $service->label);
+        }
+
         if ($service->price < 0) {
             // Negative prices are discounts
             return sprintf('%s (-%s€ Rabatt)', $service->label, number_format(abs($service->price), 2, ',', '.'));