When specifying the parameter of an `array` type, the `enum` property
needs to be set on the `items` property. So instead of:

```json
{
  "name": "...",
  "type": "array",
  "items": {
    "type": "..."
  },
  "enum": [...]

```

We should define as:

```json
{
  "name": "...",
  "type": "array",
  "items": {
    "type": "...",
    "enum": [...]
  }

```