Added Aspect-oriented Modelling guide

Author: danjoa

.vitepress/theme/custom.scss

@@ -367,7 +367,7 @@ kbd {
   margin-top: -5px;
   margin-bottom: 5px;
   display: block;
-  &, & a { color: #999 !important; .dark & { color: #777 !important }};
+  & { color: #999 !important; .dark & { color: #777 !important }};
 
   &::before {
     content: url('/images/learn-more.svg');

advanced/assets/data-model.cds

@@ -13,3 +13,7 @@ entity Chapters {
   chapterName : String;
   book        : Association to one Books on book.ID=book_ID;
 };
+
+extend entity Books with @foo:11 {
+  author : String;
+};