Add a self referential column

[silentninja]

Problem

There isn't a way to test self-referencing column features with the current dataset. Can a column with self reference reference be added?

[kgodey]

I think it would also be good to add a table with two FK references to a different table (e.g. imagine a Package table that has columns for from address and to address that are both FKs to an Address table)

[mathemancer]

@kgodey do you think we should extend the library data set, or do something different? N.b., we already have an academics data set with both features mentioned in the Mathesar testing resources directory. We could simulate a larger version of that if we want.

[kgodey]

@mathemancer I think we should have a separate data set so we don't contaminate the demo data set. I don't have a preference on extending the library data set or creating a new one. I think whatever is fastest to implement is better.