Update userguide about natural-ids

Signed-off-by: Thorsten <[email protected]>

documentation/src/main/asciidoc/userguide/chapters/domain/natural_id.adoc

@@ -8,11 +8,12 @@
 :extrasdir: extras
 
 Natural ids represent domain model unique identifiers that have a meaning in the real world too.
-Even if a natural id does not make a good primary key (surrogate keys being usually preferred), it's still useful to tell Hibernate about it.
-As we will see later, Hibernate provides a dedicated, efficient API for loading an entity by its natural id much like it offers for loading by identifier (PK).
 
 [IMPORTANT]
 ====
+NaturalId Annotations are a proprietary Hibernate feature and not a part of JPA. They should only be used
+if you intent to use NaturalIdLoadAccess, which is also a proprietary hibernate feature.
+
 All values used in a natural id must be non-nullable.
 
 For natural id mappings using a to-one association, this precludes the use of not-found