create_lookup: Create ID Lookup Table
In michaelgao8/dukeehR: Processing for EHR (Written for Duke Health)

This function creates a lookup dataframe where one column is the original key of an input dataframe and the other is the replacement ID

1	create_lookup(dataset, keycol_name, digits = 7, seed = 123)

`dataset`	The input data.frame that contains a column which is the key (unique identifier)
`keycol_name`	A string that is the name of the column that the unique id is located in
`digits`	An integer number of digits of the replacement id. The default is 7 to allow for enough entries. Note that increasing the argument too much will result in a large amount of memory used to internally store the range of all possible values.
`seed`	The random seed used to generate the dataset. This can be used to reconstruct the id mapping at a later stage.