enable etag on content field again and test with UI5 1.131 SNAPSHOT

Author: mofterdinger

app/fiori.html

@@ -14,8 +14,8 @@
 		};
 	</script>
 
-	<script id="sap-ushell-bootstrap" src="https://sapui5.hana.ondemand.com/1.129.0/test-resources/sap/ushell/bootstrap/sandbox.js"></script>
-	<script id="sap-ui-bootstrap" src="https://sapui5.hana.ondemand.com/1.129.0/resources/sap-ui-core.js"
+	<script id="sap-ushell-bootstrap" src="https://sapui5nightly.int.sap.eu2.hana.ondemand.com/test-resources/sap/ushell/bootstrap/sandbox.js"></script>
+	<script id="sap-ui-bootstrap" src="https://sapui5nightly.int.sap.eu2.hana.ondemand.com/resources/sap-ui-core.js"
 			data-sap-ui-libs="sap.m, sap.ushell, sap.collaboration, sap.ui.layout"
 			data-sap-ui-compatVersion="edge"
 			data-sap-ui-theme="sap_horizon"

db/books.cds

@@ -26,10 +26,6 @@ entity Books : cuid, managed {
     covers       : Composition of many Attachments;
 }
 
-annotate Attachments with {
-    modifiedAt @(odata.etag: null);
-}
-
 entity Authors : cuid, managed {
     @assert.format : '^\p{Lu}.*' // assert that name starts with a capital letter
     name         : String(111);