[fixes #2991] Add documentation note on mixing mapstruct and fieldnameconstants in @Mapping.

website/templates/features/experimental/FieldNameConstants.html

@@ -58,6 +58,8 @@
 			Any parameters of lombok annotations that take strings need to be supplied actual string literals; you cannot have references to constants like those generated by <code>@FieldNameConstants</code>. If you'd like to use <code>@FieldNameConstants</code> to for example fill in the <code>of</code> and/or <code>exclude</code> parameters of <code>@ToString</code> and similar lombok annotations, use the <code>@ToString.Include</code> / <code>@ToString.Exclude</code> etc system instead; these are described at the feature pages for those features.
 		</p><p>
 			Like other lombok handlers that touch fields, any field whose name starts with a dollar (<code>$</code>) symbol is skipped entirely. Such a field will not be modified at all. Static fields are also skipped.
+		</p><p>
+			<em>MapStruct interop:</em> When making references to field name constants inside MapStruct's <code>@Mapping</code>, and you use that annotation more than once on a node, you must manually wrap these in the <code>@Mappings</code> 'container annotation'. Like so: <code>@Mappings({@Mapping(target = Entity.Fields.entityProperty, source = "dtoProperty")})</code>.
 		</p>
 	</@f.smallPrint>
 </@f.scaffold>