deid_dua: Convert identifying variable to unique hash
In duawranglr: Securely Wrangle Dataset According to Data Usage Agreement

Convert a column of unique but restricted IDs into a set of new IDs using secure (SHA-2) hashing algorithm. Users have the option of saving a crosswalk between the old and new IDs in case observations need to reidentified at a later date.

deid_dua(
  df,
  id_col = NULL,
  new_id_name = "id",
  id_length = 64,
  existing_crosswalk = NULL,
  write_crosswalk = FALSE,
  crosswalk_filename = NULL
)

`df`	Data frame
`id_col`	Column name with IDs to be replaced. By default it is `NULL` and uses the value set by the `id_column` argument in `set_dua_level()` function.
`new_id_name`	New hashed ID column name, which must be different from old name.
`id_length`	Length of new hashed ID; cannot be fewer than 12 characters (default is 64 characters).
`existing_crosswalk`	File name of existing crosswalk. If existing crosswalk is used, then `new_id_name`, `id_length`, `id_length`, and `crosswalk_name` will be determined by the already existing crosswalk. Arguments given for these values will be ignored.
`write_crosswalk`	Write crosswalk between old ID and new hash ID to console (unless `crosswalk_name` is given value).
`crosswalk_filename`	Name of crosswalk file with path; defaults to generic name with current date (YYYYMMDD) appended.

## --------------
## Setup
## --------------
## set DUA crosswalk
dua_cw <- system.file('extdata', 'dua_cw.csv', package = 'duawranglr')
set_dua_cw(dua_cw)
## read in data
admin <- system.file('extdata', 'admin_data.csv', package = 'duawranglr')
df <- read_dua_file(admin)
## --------------

## show identified data
df

## deidentify
df <- deid_dua(df, id_col = 'sid', new_id_name = 'id', id_length = 12)

## show deidentified data
df

## Not run: 
## save crosswalk between old and new ids for future
deid_dua(df, write_crosswalk = TRUE)

## use existing crosswalk (good for panel datasets that need link)
deid_dua(df, existing_crosswalk = './crosswalk/master_crosswalk.csv')

## End(Not run)