How to change the unit of addDrawToolbar()'s circle's radius to meters?

Question

How can I change the unit of the circle's radius that can be drawn with the following script? It displays it in feet and I need it in kilometers. Changing it for the whole DrawToolbar would be even better.

library(shiny)
library(leaflet)
library(leaflet.extras)

ui = fluidPage(
  leafletOutput("map")
)

server = function(input,output,session){
  output$map = renderLeaflet(
leaflet()%>%
  addTiles()%>%
  addMeasure(
    primaryLengthUnit = "kilometers",
    secondaryAreaUnit = FALSE
    )%>%
  addDrawToolbar(
    targetGroup='draw',
    editOptions = editToolbarOptions(selectedPathOptions = selectedPathOptions()))  %>%
  setView(lat = 45, lng = 9, zoom = 3)
  )
}

shinyApp(ui,server)

Answer 1

It's very easy because the development version of leaflet.extras has the function. Let's copy it.
(see: https://github.com/bhaskarvk/leaflet.extras/blob/master/R/drawOptions.R).
Here is what you want.

    )%>%
  addDrawToolbar(
  targetGroup='draw',
  editOptions = editToolbarOptions(selectedPathOptions = selectedPathOptions()),
  circleOptions = filterNULL(list(shapeOptions = drawShapeOptions(),
                                  repeatMode = F,
                                  showRadius = T,
                                  metric = T,
                                  feet = F,
                                  nautic = F))) %>%