feat: Add defaults to optionSetItem [DHIS2-18643]

[maikelarabori]

We need to return a default “optionSetItem” object to keep the new option set item object backward compatible with existing Visualization and allow clients to distinguish between elements that contain an option set from elements that do not.

To achieve it we have to return something like the snippet below:

columns: [{
	dimension: 'dx',
	items: [{
		name: "Data element with option set",
		optionSetItem: { // Always return below by default, if optionSetItem or aggregation is not set
			aggregation: "AGGREGATED",
		},
	}],
}]

[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