SAP IdDS attribute from custom schema not in response payload

[Klaus1]

Hello,

I've created a custom schema for groups with the attribute sourceSystem but I'm not getting the schema and the attribute value in my response.

Schema:

Source System transformation:
"group": {
"mappings": [
{
"sourcePath": "$.id",
"targetVariable": "entityIdSourceSystem"
},
{
"targetPath": "$.schemas[0]",
"constant": "urn:ietf:params:scim:schemas:core:2.0:Group"
},
{
"targetPath": "$.schemas[1]",
"constant": "urn:sap:cloud:scim:schemas:extension:custom:2.0:Group"
},
{
"targetPath": "$.schemas[2]",
"constant": "urn:sap:cloud:scim:schemas:extension:xxxxx:2.0:Group"
},
{
"sourcePath": "$['urn:sap:cloud:scim:schemas:extension:custom:2.0:Group']['name']",
"targetPath": "$['urn:sap:cloud:scim:schemas:extension:custom:2.0:Group']['name']"
},
{
"sourcePath": "$.displayName",
"targetPath": "$.displayName"
},
{
"sourcePath": "$['urn:sap:cloud:scim:schemas:extension:xxxxx:2.0:Group']['sourceSystem']",
"targetPath": "$['urn:sap:cloud:scim:schemas:extension:xxxxx:2.0:Group']['sourceSystem']"
},
{
"sourcePath": "$.members",
"targetPath": "$.members",
"optional": true,
"preserveArrayWithSingleElement": true
}
]
}
}

api.sap.com

"Try out" in api.sap.com

Payload for response of an example group:

{
  "id": "xxxxxxxx",
  "meta": {
    "created": "2024-03-18T13:44:19Z",
    "lastModified": "2024-03-18T13:44:19Z",
    "location": "accounts.ondemand.com/scim/Groups/xxxxxxx",
    "resourceType": "Group"
  },
  "schemas": [
    "urn:ietf:params:scim:schemas:core:2.0:Group",
    "urn:sap:cloud:scim:schemas:extension:custom:2.0:Group"
  ],
  "displayName": "IBP-TEST_TEST_ROLE_1",
  "urn:sap:cloud:scim:schemas:extension:custom:2.0:Group": {
    "name": "ABC",
    "additionalId": "65f84533cfa5e50d9ea4a785"
  }
    

 There is no custom schema and no sourceSystem attribute at all.

Does anybody know what is missing?

Best regards
Klaus