Add functionality to create censored columns given truth

[athowes]

This is distinct from the "preprocessing" version (see #313). This is taken from work on PR #352 which is being scrapped. But this will be useful when we do the "simulation" side of things:

#' Add columns for interval censoring of primary and secondary events
#'
#' @param linelist ...
#' @param pwindow The primary censoring window.
#' @param swindow The secondary censoring window.
#' @family observe
#' @autoglobal
#' @export
f <- function(linelist, pwindow = 1, swindow = 1) {
  assert_numeric(pwindow, lower = 0)
  assert_numeric(swindow, lower = 0)
  
  linelist |>
    mutate(
      ptime_lwr = .floor_mult(.data$ptime, f = pwindow),
      ptime_upr = .data$ptime_lwr + pwindow,
      stime_lwr = .floor_mult(.data$stime, f = swindow),
      stime_upr = .data$stime_lwr + swindow,
      delay_lwr = pmax(0, .data$stime_lwr - .data$ptime_lwr - 1),
      delay_upr = .data$delay_lwr + pwindow + swindow
    )
}