How can I, simply, rotate a model entity?

1. A concise explanation of the problem you're experiencing.

I'd like to rotate a 3D model that I've got on the map, but nothing I have tried has worked so far. Cesium Sandbox has a rotation property on things like cubes, so I'd assume the same should apply to models? The most recent code I've tried is as below, but I've also tried making a modelMatrix with the position, but I can't figure out how to get that to rotate either.

2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.

    var plane = viewer.entities.add({
      position: Cesium.Cartesian3.fromDegrees(40.0, 100.0, 5000),
      model: {
        uri: '/models/plane.glb',
        rotation: Cesium.Math.toRadians(45)

In this example, the rotation attribute does nothing.

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

I'd like to rotate the model by a certain amount, say 45 degrees.

4. The Cesium version you're using, your operating system and browser.

Cesium 1.58.1
Firefox 68
Windows 10 17763

You can see there is no rotation property on a model here:

There is an orientation property on the entity itself, you can see how it’s used on a 3d model here:

There’s a code example showing how to rotate it over time in this GitHub issue:

Hope this helps! What kind of application are you working on?