Join lookup variables from slf postcode lookup and slf gpprac lookup.
Usage
join_slf_lookup_vars(
individual_file,
slf_postcode_lookup = read_file(get_slf_postcode_path()),
slf_gpprac_lookup = read_file(get_slf_gpprac_path(), col_select = c("gpprac",
"cluster", "hbpraccode")),
hbrescode_var = "hb2018"
)