feat: status-transition flows (#15)

### summary

makes use of new status-transition flows feature of cds-services^4.5 and
cds^9.5:
- check entry state(s) for action → previously unchecked → TODO: true?
- set to exit state for action → remove custom handlers
- automatically add ui artifacts → remove unnecessary annotations

### `CDS_ENV=flow mvn cds:watch`

extends to a more complex flow incl. usage of `@to: $flow.previous`.
for that, status `InReview` and `Blocked` as well as actions
`reviewTravel`, `reopenTravel`, `blockTravel`, and `unblockTravel` were
added in order to create a scenario where the previous state of
`Blocked` can be either `Open` or `InReview`.

visualization of the flow:
<img width="913" height="444" alt="image"
src="https://github.com/user-attachments/assets/8dd98cdf-7a01-4e55-85bc-a2a7d69fdd16"
/>

---

### related

- capire/xtravels#12

Author: sjvans

.cdsrc.json

@@ -1,5 +1,7 @@
 {
-  "features": {
-    "compile_for_flows": true
+  "[flow]": {
+    "folders": {
+      "flow": "xmpls/flow/"
+    }
   }
 }

README.md

@@ -114,6 +114,10 @@ Alternatively start the application on the command line by executing:
 mvn spring-boot:run -Dspring-boot.run.profiles=default,hybrid
 ```
 
+## Additional Examples
+
+For more (extensive) examples, have a look at the [readme file in the xmpls folder](./xmpls/readme.md).
+
 ## License
 
 Copyright (c) 2025 SAP SE or an SAP affiliate company. All rights reserved. This file is licensed under the Apache Software License, version 2.0 except as noted otherwise in the [LICENSE](LICENSE) file.

_i18n/i18n_en.properties

@@ -3,6 +3,7 @@ Agency=Agency
 AgencyName=Agency Name
 AvgPrice=Average Price
 BeginDate=Starting Date
+BlockTravel=Block Travel
 Booking=Booking
 BookingDate=Booking Date
 BookingDetails=Booking Details
@@ -36,6 +37,8 @@ Prices=Prices
 ProductID=Product
 ProductPrice=Product Price
 RejectTravel=Reject Travel
+ReopenTravel=Reopen Travel
+ReviewTravel=Review Travel
 Status=Status
 Street=Street
 Title=Title
@@ -45,4 +48,5 @@ Travel=Travel
 TravelAgency=Travel Agency
 Travels=Travels
 TravelStatus=Travel Status
+UnblockTravel=Unblock Travel
 WebAddress=Web Address

app/labels.cds

@@ -74,6 +74,16 @@ annotate schema.Passengers with @title: '{i18n>Passenger}' {
 }
 
 
+using { TravelService } from '../srv/travel-service';
+
+annotate TravelService.Travels with actions {
+  rejectTravel    @title: '{i18n>RejectTravel}';
+  acceptTravel    @title: '{i18n>AcceptTravel}';
+  reopenTravel    @title: '{i18n>ReopenTravel}';
+  deductDiscount  @title: '{i18n>DeductDiscount}';
+};
+
+
 using sap.capire.flights.data;
 
 annotate data.Airlines with @title: '{i18n>Airline}' {

app/travels/field-control.cds

@@ -14,15 +14,10 @@ annotate TravelService.Travels with @(Common : {
   EndDate     @readonly: (Status.code = #Accepted) @mandatory: (Status.code != #Accepted);
   Agency      @readonly: (Status.code = #Accepted) @mandatory: (Status.code != #Accepted);
   Customer    @readonly: (Status.code = #Accepted) @mandatory: (Status.code != #Accepted);
-
 } actions {
-  rejectTravel @from: [#Open, #Accepted];
-  acceptTravel @from: [#Open, #Canceled];
   deductDiscount @(
-    from: #Open,
     Common.SideEffects.TargetProperties : ['in/TotalPrice', 'in/BookingFee'],
   );
-  draftEdit @from: [#Open, #Accepted]
 }
 
 annotate TravelService.Travels @Common.SideEffects#ReactonItemCreationOrDeletion : {

app/travels/layouts.cds

@@ -7,9 +7,7 @@ using { TravelService } from '../../srv/travel-service';
 annotate TravelService.Travels with @UI : {
 
   Identification : [
-    { $Type  : 'UI.DataFieldForAction', Action : 'TravelService.acceptTravel',   Label  : '{i18n>AcceptTravel}'   },
-    { $Type  : 'UI.DataFieldForAction', Action : 'TravelService.rejectTravel',   Label  : '{i18n>RejectTravel}'   },
-    { $Type  : 'UI.DataFieldForAction', Action : 'TravelService.deductDiscount', Label  : '{i18n>DeductDiscount}' }
+    { $Type  : 'UI.DataFieldForAction', Action : 'TravelService.deductDiscount', Label  : '{i18n>DeductDiscount}' },
   ],
 
   HeaderInfo : {
@@ -35,8 +33,6 @@ annotate TravelService.Travels with @UI : {
 
   LineItem : [
 
-    { $Type  : 'UI.DataFieldForAction', Action : 'TravelService.acceptTravel',   Label  : '{i18n>AcceptTravel}'   },
-    { $Type  : 'UI.DataFieldForAction', Action : 'TravelService.rejectTravel',   Label  : '{i18n>RejectTravel}'   },
     { $Type  : 'UI.DataFieldForAction', Action : 'TravelService.deductDiscount', Label  : '{i18n>DeductDiscount}' },
 
     { Value : ID,            @UI.Importance : #High },
@@ -50,8 +46,8 @@ annotate TravelService.Travels with @UI : {
     { Value : (Status.code),
       Criticality : (
         Status.code == #Accepted ? 3 :
-        Status.code == #Open ? 2 :
-        Status.code == #Canceled ? 1 : 0
+        Status.code == #Open OR Status.code == #InReview ? 2 :
+        Status.code == #Canceled OR Status.code == #Blocked ? 1 : 0
       ),
       @UI.Importance : #High,
       @HTML5.CssDefaults: {width:'10em'}
@@ -74,8 +70,8 @@ annotate TravelService.Travels with @UI : {
     { Value : (Status.code),
       Criticality : (
         Status.code == #Accepted ? 3 :
-        Status.code == #Open ? 2 :
-        Status.code == #Canceled ? 1 : 0
+        Status.code == #Open OR Status.code == #InReview ? 2 :
+        Status.code == #Canceled OR Status.code == #Blocked ? 1 : 0
       ),
     },
     { Value : BeginDate },

db/data/sap.capire.travels-TravelStatus.csv

@@ -1,4 +1,6 @@
 code;name
 O;Open
+R;InReview
+B;Blocked
 A;Accepted
 X;Canceled