Allow unique keys as foreign keys

Hi!

In this blog post you state that "the primary-key column(s) in the parent MUST necessarily be reflected as a foreign-key in the child table", indicating the reason why when creating a relationship, SqlDBM automatically assumes the parent PK as the child's FK.

This is not correct, however, since any unique key in the parent can be used to define a relationship. It would be great if you could address this issue, please, as it currently stops our team from fully adopting this otherwise amazing tool.

Best regards,

Igor Rocha