Alternate ways to render a controller action output

We may need to do something more complex than opening a popup with some static text. Maybe we can show more data about a specific weather forecast, such as pressure, humidity, and wind speed.

We need to define a new controller action to render the details of a forecast for a specific city at a specific date and time. The controller action will use a new theme hook to render a set of detailed information:

function alps_weather_theme(): array {
  return [
    [...]
    'alps_weather_details' => [
      'variables' => [
        'forecast' => [],
        'units' => 'metric',
      ],
    ],
  ];
}

The alps_weather_details theme hook takes the same variables...