feat: add lighthouse serializer utils

api/src/backend/api/v1/serializer_utils/lighthouse.py

@@ -0,0 +1,13 @@
+import re
+
+from rest_framework_json_api import serializers
+
+
+class OpenAICredentialsSerializer(serializers.Serializer):
+    api_key = serializers.CharField()
+
+    def validate_api_key(self, value: str) -> str:
+        pattern = r"^sk-[\w-]+$"
+        if not re.match(pattern, value or ""):
+            raise serializers.ValidationError("Invalid OpenAI API key format.")
+        return value