How do I receive CSV file using Plumber API to send back a report?

Question

I am currently working on a project involving a Plumber API, and I've encountered a challenge related to handling CSV files sent to the API.

I have a Plumber API where I need to receive two CSV files sent from Postman (for example) then they're used to generate a report that would be downloaded. I am unsure how to do that.

I found some helpful info about using mime package to do that in here: https://github.com/krlmlr/plumber-uploader/tree/f-multipart

I tried replicating that but it's still not working : "error 500"

Here's my code :

serializer_word <- function (..., type = "application/vnd.openxmlformats-officedocument.wordprocessingml.document") 
{
  serializer_content_type(type, function(val) {
    val
  })
}

register_serializer("word", serializer_word)

#* create a report
#* @serializer word
#* @post /generate_report_from_data
upload <- function(req, res) {
  
  multipart <- mime::parse_multipart(req)

  uploaded_file1 <- multipart$upload[[1]]
  uploaded_file2 <- multipart$upload[[2]]

  in_file1 <- uploaded_file1$name
  out_file1 <- uploaded_file1$datapath
  df <- read.csv(in_file1, header = TRUE, sep = ";")  

  in_file2 <- uploaded_file2$name
  out_file2 <- uploaded_file2$datapath
  df_bbl <- read.csv(in_file2, header = TRUE, sep = ";")  
  
  df <- data_recoding(df, df_bbl, sep = ",")
  
  team1 <- df
  team2 <- df_bbl
  
  output_path <- paste0(getwd(), "/rapport_.docx")
  
  rmarkdown::render("rapport_.Rmd", 
                    output_file = output_path, 
                    output_format = word_document(reference_docx = "tmplt.docx"),
                    params = list(team1 = team1, team2 = team2))
  
  
  file_content <- readBin(output_path, "raw", n = file.info(output_path)$size)
  
  res$status <- 200
  res$body <- as_attachment(file_content, "rapport_.docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document")
}