dos: add docs on overriding allowed fields in routes (#12233)

www/apps/book/app/learn/customization/extend-features/query-linked-records/page.mdx

@@ -31,7 +31,7 @@ Medusa's existing API routes accept a `fields` query parameter that allows you t
 
 <Note>
 
-Learn more about selecting fields and relations in the [API Reference](!api!/admin#select-fields-and-relations).
+Learn more about using the `fields` query parameter to retrieve custom linked data models in the [Retrieve Custom Linked Data Models from Medusa's API Routes](../../../fundamentals/api-routes/retrieve-custom-links/page.mdx) chapter.
 
 </Note>