/// Pure function mapping new state to a new `TableViewModel`.  This is invoked each time the state updates
/// in order for ReactiveLists to update the UI.
static func viewModel(forState groups: [ToolGroup]) -> TableViewModel {
    // Create a section for every tool group
    let sections: [TableSectionViewModel] = groups.map { group in
        // Create a single cell for every tool
        let cellViewModels = group.tools.map { ToolTableCellModel(tool: $0) }
        return TableSectionViewModel(
            headerTitle: group.name,
            headerHeight: 44,
            cellViewModels: cellViewModels,
            diffingKey: group.name
        )
    }
    return TableViewModel(sectionModels: sections)
}