Display raster over shapefile in shiny R

Question

I am trying to display a raster over my shapefile in my shiny app. Here's my approach.

# Load libraries and create sample data 

  library(raster)
  library(shiny)
  library(dplyr)
  library(leaflet)
  library(ggplot2)
  library(ggthemes)
  library(tmap)

  fr.shp <- getData('GADM', country='FRA', level=1)

  coords <- data.frame(coordinates(fr.shp))
  names(coords) <- c('lon', 'lat')
  dat.df <- expand.grid(lon = coords[, 1],
                        seasonID = c('winter', 'summer'),
                        business = c('train', 'bus', 'taxi'), 
                        variable = c('modP', 'modT'),
                        YearRef = 2001:2003)

  dat.df1 <- coords %>% dplyr::left_join(dat.df) %>% dplyr::mutate(value = rnorm(n()))

Below is my shiny app that shows the values for a given combination of seasonID, businees, variable and YearRef. The code that I have commented out was supposed to also plot the shapefile over which the raster should be plotted. However it is not working.

  ui <- fluidPage(
        titlePanel('my shiny'),
          sidebarLayout(position = 'left',
              sidebarPanel(
                selectInput(inputId = 'seasonRef', label = 'Select season', choices = c('winter','summer'), selected = 'Kharif'),
                selectInput(inputId = 'transport', label = 'Select transport',
                            choices = c('train','bus','taxi'), selected = 'train'),
                checkboxGroupInput(inputId = 'type', label = NULL, 
                                   choiceNames = c('modP','modT'),
                                   choiceValues = c('modP','modT'),
                                   width = '400px', selected = 'modP'),
                sliderInput('yearRef','Select Year',min=2001,max=2003,value=1)
                ),

                mainPanel(
                  tabsetPanel(
                  tabPanel('myplots', plotOutput(outputId = 'rast')),
                  leafletOutput("my_tmap")
                )
                )
              )
          )

    server <- function(input, output) {

        tempI <- reactive({dat.df1 %>% dplyr::filter(seasonID == input$seasonRef &
                                                     business == input$transport &
                                                     YearRef == input$yearRef &
                                                     variable == input$type)})

        output$rast <- renderPlot({
        ggplot() + geom_raster(data = tempI(), aes(x = lon, y = lat, fill = value)) +
        theme_map() + coord_equal() + scale_fill_viridis_c(option = 'C')
      })

        # tmap_mode("view")
        #  output$my_tmap = renderLeaflet({
        #    qtm(fr.shp)})
      }


      shinyApp(ui, server)

I show this question but this only lets a background shapefile to be used instead of my own shapefile.

Overlaying shapefiles or raster over interactive maps