[feat] add user and add event

backend/project/api/users/serializers.py

@@ -0,0 +1,24 @@
+from rest_framework import serializers
+
+from api.events.models import Event
+from api.users.models import User
+
+
+class UserSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = User
+        fields = "__all__"
+
+    def create(self, validated_data):
+        try:
+            event = Event.objects.get(
+                pk=self.context["view"].kwargs.get("event_id")
+            )
+        except Event.DoesNotExist as e:
+            msg = "Event does not exist"
+            raise serializers.ValidationError(msg) from e
+
+        user = User.objects.create(**validated_data)
+        event.users.add(user)
+
+        return user