fix: Restrict data exchange request data items to allowable types only

[jason-p-pickering]

Fixes https://dhis2.atlassian.net/browse/DHIS2-20860 on the backend.

Does not deal with existing exchanges which might have non-allowable data item types, but since these are not expected to work in practice anyway, users should be able to resolve this.

Changes

• Add E6306 error code for unsupported data item types in aggregate data exchange requests
• Validate dx item types in AggregateDataExchangeObjectBundleHook using DimensionService to resolve each item and check its type against the allowed set
• Add unit tests for disallowed types (REPORTING_RATE, PROGRAM_DATA_ELEMENT) and allowed types

Test plan

• Existing unit tests pass (14/14)
• Verified from the UI

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud