Introduced bookstore composite app

bookstore/db/hana/index.cds

@@ -0,0 +1,10 @@
+//
+//  Add Author.age and .lifetime with a DB-specific function
+//
+
+using { AdminService } from '../schema';
+
+extend projection AdminService.Authors with {
+  YEARS_BETWEEN(dateOfBirth, dateOfDeath)         as age: Integer,
+  YEAR(dateOfBirth) || ' – ' || YEAR(dateOfDeath) as lifetime : String
+}