[fix]

backend/project/api/events/serializers.py

@@ -1,9 +1,18 @@
 from rest_framework import serializers
 
-from api.events.models import Event
+from api.events.models import Event, Tree
 
 
 class EventSerializer(serializers.ModelSerializer):
+    tree = serializers.IntegerField(write_only=True)
+
     class Meta:
         model = Event
         fields = "__all__"
+
+    def create(self, validated_data):
+        tree = Tree.objects.get_or_create(pk=validated_data.pop("tree"))
+
+        validated_data["tree"] = tree.id
+
+        return Event.objects.create(**validated_data)