docs: Document custom header support for Table Topic REST catalogs

core/src/test/java/kafka/automq/table/CatalogFactoryTest.java

@@ -143,4 +143,4 @@ public void close() {
             catalogBackend.stop(0);
         }
     }
-}
+}

docs/table-topic-custom-headers.md

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+# Custom Headers for Table Topic REST Catalogs
+
+AutoMQ Table Topic supports custom HTTP headers for REST catalog integrations, enabling integration with catalog services that require specific headers.
+
+## Configuration Pattern
+
+Custom headers can be configured using the following pattern:
+
+```properties
+automq.table.topic.catalog.header.{header-name}={header-value}
+```
+
+Where:
+- `{header-name}` is the HTTP header name (case-sensitive)
+- `{header-value}` is the header value
+
+## Common Use Cases
+
+- **Authentication**: Bearer tokens, API keys
+- **Multi-tenant environments**: Tenant identification headers
+- **Apache Polaris integration**: Realm-specific headers
+- **Custom routing**: Load balancer or service routing headers
+
+## Example Configuration
+
+```properties
+# Basic REST catalog configuration
+automq.table.topic.catalog.type=rest
+automq.table.topic.catalog.uri=http://your-catalog-server:8181
+automq.table.topic.catalog.warehouse=s3://your-bucket/iceberg
+
+# Custom headers
+automq.table.topic.catalog.header.Authorization=Bearer your-token
+automq.table.topic.catalog.header.X-Custom-Header=custom-value
+```
+
+## Integration Examples
+
+For detailed integration examples, including:
+- Apache Polaris setup with docker-compose
+- Authentication configurations
+- Troubleshooting guides
+
+Visit the [AutoMQ Labs repository](https://github.com/AutoMQ/automq-labs/tree/main/table-topic-solutions).
+
+## Supported Catalog Types
+
+Custom headers are supported only for REST catalogs (`automq.table.topic.catalog.type=rest`).