check if file is available at a url

[NewGraphEnvironment]

need to see how we can give informative error messages if url is incorrectly entered or if there are no files at the urls we are trying to hit

here is a true false start

is_valid_url <- function(url) {
  # Regular expression for a simple URL validation
  pattern <- "^https?://[a-zA-Z0-9\\-\\.]+\\.[a-zA-Z]{2,}(/\\S*)?$"
  grepl(pattern, url)
}

is_accessible_url <- function(url) {
  response <- httr::HEAD(url)
  status <- httr::status_code(response)
  status == 200
}