I see no reason why there couldn't be more than one `online` option - might as well allow for an array

```
"online": {
  "description": "Online location(s) of opportunity. Could be a sign up link.",
  "oneOf": [
    {
      "type": "string",
      "format": "uri"
    },
    {
      "type": "array",
      "uniqueItems": true,
      "minItems": 1,
      "items": { "$ref": "#/definitions/online/oneOf/0" }
    }
  ]
}
```