Identifying exit numbers in roundabouts

Mapbox Navigation SDK version: 2.0.0-rc.2

https://hey.mapbox.com/directions-debug/#route=6.124388228364182,45.9055553186453;6.126108200540244,45.90652815414734&server=https://api.mapbox.com&profile=mapbox/driving-traffic&style=empty&queryparams=steps%3Dtrue%26overview%3Dfull%26geometries%3Dgeojson%26roundabout_exits%3Dtrue%26voice_units%3Dimperial%26voice_instructions%3Dtrue&token=pk.eyJ1Ijoic3ZjLW9rdGEtbWFwYm94LXN0YWZmLWFjY2VzcyIsImEiOiJja2d0bHMxbDcwNHI0MnRxbHBwNTBoeHN0In0.X5Gn0apaqXAXDkZ1sSDLfA

Directions API provides an exit number

              "maneuver": {
                "type": "roundabout",
                "exit": 3,
                "instruction": "Enter the roundabout and take the 3rd exit onto Avenue de Brogny/D 1201.",
                "modifier": "slight right",
                "bearing_after": 123,
                "bearing_before": 94,
                "location": [
                  6.125695,
                  45.90563
                ]
              },

But I can't find this exit number from the navigation-ui Maneuver api. It seems like it should be near the "degrees"

Here's the definition we're looking to satisfy for Android Auto from their Manevuer.setRoundaboutExitNumber

For example, if the driver is joining a counter-clockwise roundabout with 4 exits,
then the exit to the right would be exit #1, the one straight ahead would be exit #2,
the one to the left would be exit #3 and the one used by the driver to join the
roundabout would be exit #4.

cc: @cafesilencio @abhishek1508 @Guardiola31337

Directions API のラウンドアバウト マヌーバー データと、issue にリンクされている PrimaryManeuver.kt の定義から始めます。マヌーバーのフィールドが navigation-ui Maneuver API に到達するまでの流れを追跡し、Android Auto Maneuver.setRoundaboutExitNumber の定義を使ってラウンドアバウトの出口番号を公開します。要求された出口番号がこのルートで利用可能になれば完了です。