Initial Python rewrite

src.bak/main/java/com/example/util/FirestoreTimestampSerializer.java

@@ -0,0 +1,35 @@
+/*
+* Copyright 2025 Google. This software is provided as-is, without warranty or representation for any use or purpose.
+* Your use of it is subject to your agreement with Google.
+*/
+
+package com.example.util;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.google.cloud.Timestamp;
+import java.io.IOException;
+
+/**
+ * Custom Jackson Serializer for com.google.cloud.Timestamp.
+ * This is crucial for ObjectMapper.convertValue to correctly handle Timestamp objects
+ * when they are encountered in a Map<String, Object> and need to be internally
+ * serialized before deserialization into a DTO. It converts Timestamp into a
+ * simple JSON object with "seconds" and "nanos" fields.
+ */
+public class FirestoreTimestampSerializer extends JsonSerializer<Timestamp> {
+
+    @Override
+    public void serialize(Timestamp value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
+        if (value == null) {
+            gen.writeNull();
+        } else {
+            // Write Timestamp as a JSON object with seconds and nanos
+            gen.writeStartObject();
+            gen.writeNumberField("seconds", value.getSeconds());
+            gen.writeNumberField("nanos", value.getNanos());
+            gen.writeEndObject();
+        }
+    }
+}