fix: update odata example to use constant reference for ServiceUrl

ServiceUrl must be a constant reference (@Module.Const), not a string
literal. Added OdTest.FullConfigAPIServiceUrl constant and updated the
example to reference it, matching the new CE6825 validation.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ako

mdl-examples/doctype-tests/10-odata-examples.mdl

@@ -228,14 +228,18 @@ DEFAULT 'proxy.example.com';
 CREATE CONSTANT OdTest.ProxyPortConst
 TYPE String
 DEFAULT '8080';
+
+CREATE CONSTANT OdTest.FullConfigAPIServiceUrl
+TYPE String
+DEFAULT 'https://api.example.com/odata/v4';
 /
 
 CREATE ODATA CLIENT OdTest.FullConfigAPI (
   Version: '3.0',
   ODataVersion: OData4,
   MetadataUrl: 'https://api.example.com/odata/v4/$metadata',
   Timeout: 300,
-  ServiceUrl: 'https://api.example.com/odata/v4',
+  ServiceUrl: @OdTest.FullConfigAPIServiceUrl,
   UseAuthentication: Yes,
   HttpUsername: 'admin',
   HttpPassword: 'secret',