store_new_submissions copies new files from the subdirectories of submissions_dir to the respective subdirectories of hist_dir. Each team has a subdirectory. The copied files in hist_dir are prefixed with the last modification date for uniqueness. A file is considered new if its name and last modification time is new, i.e not present in hist_dir. The files must match pattern regular expression and must not throw errors or warnings when given to the valid_fun function.

store_new_submissions(submissions_dir = "submissions", hist_dir = "history",
  deadline, pattern = ".*\\.csv$", valid_fun)


string. directory of the submissions. contains one subdirectory per team
string. directory where to store the history of the submissions. contains one subdirectory per team
POSIXct. deadline time for submissions. The files with last modification date after the deadline are skipped.
string. regular expression that new submission files must match (with
function that reads a submission file and throws errors or warnings if it is not valid.


store_new_submissions returns a named list of errors or warnings catched during the process. Members named after the team names are lists with members named after the file that throws an error which contain the error object.