dm_disambiguate_cols() should optionally support the use RHS of column names for joins

[krlmlr]

Need to check what this example (and perhaps others) looks like after #662.

library(dm)
#> 
#> Attaching package: 'dm'
#> The following object is masked from 'package:stats':
#> 
#>     filter
library(tidyverse)

person <- tibble(id = 1, person = "Joe")
hobby <- tibble(id = 1:2, person_id = 1, hobby = c("R Programming", "Basketball"))

dm <-
  dm(person, hobby) %>%
  dm_add_pk(person, id) %>%
  dm_add_pk(hobby, id) %>%
  dm_add_fk(hobby, id, person, id)

dm %>%
  dm_disambiguate_cols() %>%
  dm_flatten_to_tbl(hobby)
#> # A tibble: 2 × 4
#>      id person_id hobby         person
#>   <dbl>     <dbl> <chr>         <chr> 
#> 1     1         1 R Programming Joe   
#> 2     2         1 Basketball    <NA>

^{Created on 2021-10-27 by the reprex package (v2.0.1)}