How to share `ChartLegends` among multiple `BoxWhiskerChart`s in `GraphicsGrid`?

Question

First, create two BoxWhiskerChart: box1 and box2

data = { {{1, 2, 5}, {7, 2}},  {{5, 7, 2, 2, 5}, {7, 2, 5}} }
style = Sequence[{
  {"Whiskers", Dashed},
  {"Outliers", None},
  {"MedianMarker", 1, Directive[White]}},
  ChartStyle -> 56,
  ImageSize -> Medium,
  ChartLabels -> {{"A", "B", "C"}, None}];

box1 = BoxWhiskerChart[data, style]
box2 = BoxWhiskerChart[data, style]

Then put them together using GraphicsGrid and add ChartLegends for them using Legended:

boxes = Legended[
  GraphicsGrid[{{Graphics[box1], Graphics[box2]}}],
  ChartLegends -> Placed[{"x", "y"}, "Row"] ]

However, it does not produce the legends:

How to share ChartLegends among multiple BoxWhiskerCharts in GraphicsGrid?

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Related post:

I have encountered a similar problem How to share LineLegend among sub-figures in GraphicsGrid?. However, the answer there does not work here.

Answer 1

The code from the previous question's answer seems to work just as well here with the use of SwatchLegend:

Legended[GraphicsGrid[{{Graphics[box1], Graphics[box2]}}], 
 Placed[SwatchLegend[56, {"A", "B"}, LegendLayout -> "Row"], Above]]