Schema support for discriminated union types for array-items

[adierkens]

We have a use-case where the data-model represents an array with a type discriminate:

{
  pets: [
    { type: 'cat' },
    { type: 'dog', breed: 'poodle' }
  ]
}

However, there isn't a good way to represent the inclusion of the breed property on only a specific item-type in the pets array, like you could in TypeScript. This requires schema support for discriminated unions.