MapboxSearch.SearchResultMetadata values are all nil

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The received results from the following function contain no metadata for all categories.

```swift
func categorySearchResultsReceived(category: SearchCategory, results: [SearchResult]) {}
```

Here's an example of a restaurant's metadata:

`MapboxSearch.SearchResultMetadata(data: ["iso_3166_2": "GB-ENG", "iso_3166_1": "gb"], primaryImage: nil, otherImages: nil, phone: nil, website: nil, reviewCount: nil, averageRating: nil, openHours: nil)`

Here's the configuration of the search box.

```swift
lazy var searchController: MapboxSearchController = {
var configuration = Configuration(hideCategorySlots: true)
return MapboxSearchController(configuration: configuration)
}()
lazy var panelController = MapboxPanelController(rootViewController: searchController)
```

I'm using Mapbox search 1.0.0-rc.8. Am I missing something in the configuration?

Start with the categorySearchResultsReceived callback and the MapboxSearchController Configuration shown in the report, reproducing the issue on Mapbox Search 1.0.0-rc.8. Trace why SearchResultMetadata contains only the ISO country fields and determine whether configuration affects the remaining metadata. Done means the relevant metadata is populated for category search results or the missing-data behavior is documented and covered by an appropriate regression check.

Written by the indexing model from the issue text.