fiori: add warning to protect partial updates (#2641)

Co-authored-by: René Jeglinsky <rene.jeglinsky@sap.com>

Author: johannes-vogel

guides/uis/fiori.md

@@ -359,6 +359,9 @@ While this was always possible in CAP Java before, it's available for CAP Node.j
 > Directly updating an active entity does **not** bypass [draft locks](#draft-locks).
 > If an existing draft locks the entity, direct updates are blocked to prevent lost update situations.
 
+> [!warning] Ensure validation for all entry points
+> Requests to active data also features partial CREATE/UPDATE requests to the root entity and its composition children. Ensure that the validations and determinations are run in all situations, not only on the root.
+
 #### Draft-agnostic Requests
 
 Taking this further, through <Config>cds.fiori.draft_new_action: true</Config> `IsActiveEntity=true` is assumed by default, so clients that are unaware of drafts or don't need to handle them can ignore all draft-specific requests and parameters: