Update custom-format-templating.md

Author: mrtnzlml

docs/learn/export-pipeline/custom-format-templating.md

@@ -5,7 +5,6 @@ sidebar_position: 2
 ---
 
 import WebhookEndpoints from '../\_webhook_endpoints.md';
-import WIP from '../\_wip.md';
 
 # Custom format templating
 
@@ -34,10 +33,6 @@ import WIP from '../\_wip.md';
   jp="https://shared-jp.custom-format-templating.rossum-ext.app/"
 />
 
-## Basic usage
-
-<WIP issue="https://github.com/rossumai/university/issues/382" />
-
 ## Available configuration options
 
 ```json
@@ -77,6 +72,12 @@ Maximum five export configs can be defined per annotation export.
 
 :::
 
+:::warning
+
+It is important to **sanitize fields** used in the template (remove new lines, special characters, etc. so that these special characters conform to the expected format specification). It is not possible to control the whole document format so the sanitization must be performed on a field-by-field basis.
+
+:::
+
 ## Obtaining generated files
 
 Outputs from the **Custom format templating** webhook are not available anywhere in the UI. Instead, they are stored as a "[document relation](https://elis.rossum.ai/api/docs/#document-relation)". To get the actual document content, you need to call two API endpoints. First, you need to get the relevant relation: