id,node_id,number,state,locked,title,user,body,created_at,updated_at,closed_at,merged_at,merge_commit_sha,assignee,milestone,draft,head,base,author_association,repo,url,merged_by,auto_merge
1215742203,PR_kwDOBm6k_c5IdsD7,2003,open,0,Show referring tables and rows when the referring foreign key is compound,536941,"sqlite foreign keys can be compound, but that is not as well supported by datasette as single column foreign keys.

in particular, 

1. in a table view, there is not a link from the row to the referenced row if the foreign key is compound
2. in a row view, there is no listing of tables and rows that refer to the focal row if those referencing foreign keys are compound.

Both of these issues are discussed in #1099. 

This PR only fixes the second one, because it's not clear what the right UX is for the first issue.

![Screenshot 2023-01-24 at 19-47-40 nlrb bargaining_unit](https://user-images.githubusercontent.com/536941/214454749-d53deead-4151-4329-a5d4-8a7a454de7d3.png)

Some things that might not be desirable about this approach.

1. it changes the external API, by changing `column` => `columns` and `other_column` => `other_columns` (see inline comment for more discussion.
2. There are various places where the plural foreign keys have to be checked for length and discarded or transformed to singular. 
",2023-01-24T21:31:31Z,2023-01-25T18:44:42Z,,,fb3abeceb2785a582d2c120c7c1bf7dc3cd1de05,,,0,1e5b42f9d6490926300953837cbaa571ef81d772,e4ebef082de90db4e1b8527abc0d582b7ae0bc9d,CONTRIBUTOR,107914493,https://github.com/simonw/datasette/pull/2003,,