Composite foreign keys don't show up anywhere in the table structure.

Taking the following tables:

```
create table a (id1 int, id2 int, primary key (id1, id2));
create table b (id1 int, id2 int, foreign key (id1, id2) references a (id1, id2));
```

Looking at table `b` structure in postico doesn't show the foreign key that references table a.

Reproduce the report using the SQL for tables a and b, then inspect table b's structure view and the code that gathers and displays foreign keys. Done means the composite foreign key from b(id1, id2) to a(id1, id2) appears in Postico's table structure.

Written by the indexing model from the issue text.