Deploy on BTP (#793)

minimal changes required to deploy the CAP samples in _shared db_ mode:
- db: all bookshop, orders, reviews CDS models into one db instance (_shared-db_)
- services: bookstore, orders, reviews
- approuter with UI symlinks:
  - Vue: bookshop, reviews
  - Fiori: orders
 - authentification: xsuaa
 - messaging: Event Mesh
 - destinations: orders, reviews
- cds:
  - projection OrdersNoDraft for backend direct access
  - event OrderChanged
- deployment: mta.yml

shared-db/db/index.cds

@@ -0,0 +1,3 @@
+using from '@capire/bookstore';
+using from '@capire/reviews';
+using from '@capire/orders';