Should we make it harder to add properties to Resources?

[theunrepentantgeek]

Describe the current behavior

In PR #1558 we added the ability for Resources to have arbitary properties, over and above the Spec and Status properties that are standard.

Adding more properties should be a rare event - we believe that it goes against the usual good-practice convensions for Kubernetes custom resources - but nothing in the code as it stands makes this difficult.

Should we add a speed-bump to encourage future maintainers (which includes ourselves) to reconsider before additional properties are included?

Describe the improvement

We could, for example, add a check that only properties of specific names are permitted - with documentation in the code about why extending the list is almost certainly not what you want to do.