feat: add check-in REST API

backend/checkins/serializers.py

@@ -0,0 +1,31 @@
+from rest_framework import serializers
+
+
+class CheckInTokenSerializer(serializers.Serializer):
+    token = serializers.CharField(trim_whitespace=True, allow_blank=False)
+
+    def validate(self, attrs):
+        unknown_fields = set(self.initial_data) - set(self.fields)
+        if unknown_fields:
+            raise serializers.ValidationError(
+                {field: ["Unexpected field."] for field in sorted(unknown_fields)}
+            )
+        return attrs
+
+
+class CheckInPreviewResponseSerializer(serializers.Serializer):
+    status = serializers.CharField()
+    reservation_id = serializers.IntegerField()
+    performance_id = serializers.IntegerField()
+    show_title = serializers.CharField()
+    starts_at = serializers.DateTimeField()
+    party_size = serializers.IntegerField()
+
+
+class CheckInConfirmResponseSerializer(serializers.Serializer):
+    status = serializers.CharField()
+    reservation_id = serializers.IntegerField(source="preview.reservation_id")
+    performance_id = serializers.IntegerField(source="preview.performance_id")
+    party_size = serializers.IntegerField(source="preview.party_size")
+    checked_in_at = serializers.DateTimeField(source="check_in.checked_in_at")
+    checked_in_by = serializers.IntegerField(source="check_in.checked_in_by_id")