Many REST APIs return different response *types* based on result count

Brief description of your issue

I just hit upon something in the REST api that I believe we should consider changing at the schema/interface level. Some of the APIs return different result types depending on the count of items returned, for example:

        return packages.Items.Count switch
        {
            0 => new NoContentResult(),
            1 => new ApiObjectResult(new ApiResponse<Package>(packages.Items.First(), packages.ContinuationToken)),
            _ => new ApiObjectResult(new ApiResponse<List<Package>>(packages.Items.ToList(), packages.ContinuationToken)),
        };

Either No Content (null), a single object, or an array. For example:

This returns an array: .../api/packages/Microsoft.PowerToys/versions

{"Data":[{...},{...},,…],"ContinuationToken":"…"}

This returns a single object: .../api/packages/Zwift.Zwift/versions

{"Data":{...}}

This returns 204 (null): .../api/packages/Foo.Bar/versions

If the query returns more than one result, I get an object where Data is an array (and there’s a continuationToken property), but if there’s only one result, then Data is an object. This is true for the packages, packageManifests, locales, installers and versions APIs.

IMO this is a bad practice and requires clients to try to parse the result object twice in a catch block to successfully deserialize it. Instead we should always consistently return the same object type, potentially with only one item in the array, and a null continuationToken.

Steps to reproduce

Call above APIs

Expected behavior

Response type should be consistent regardless of # of results

Actual behavior

Response type varies based on number of results

Environment

N/A

Start by tracing the response handling represented by the packages.Items count switch, then inspect the packages, packageManifests, locales, installers, and versions API endpoints. Compare responses for zero, one, and multiple results. Done means each endpoint uses one consistent response shape, with behavior verified through the relevant API checks or tests.