The answer below could probably help you understand plumber parsers?
A solution similar to this?
#* Process two files in the request body
#* @post /process_files
#* @param files:[file]
#* @parser multi
#* @parser csv
function(files, req, res) {
if (length(files) < 2) {
res$status <- 400
res$body <- '{"error": "Two files must be included in the request."}'
return()
}
file1 <- files[[1]]
file2 <- files[[2]]
## here I process the data
res$status <- 200
res$body <- '{"message": "Files processed successfully."}'
}