Allow composite foreign keys

[mival]

Context

Using table backend on active record (postgres)

Expected Behavior

In translation method allow usage of compound foreign key, eg. article_type, article_id to eliminate usage extra unique column

Actual Behavior

Method crash on

1. symbolizing keys
2. joining table

Possible Fix

1. check foreign key option for array, symbolize each item
2. check foreign key option for array create JOIN with AND SQL