Graph Discussion (Temporary)

Since commenting directly on lines in github is easier than anything else I can think of, I'm opening this PR to pass feedback to @mtbc. I've marked it "exclude" and it will likely be closed quite soon. ~Josh.

--exclude
Alternatively, we can set them to `NOT NULL` in the model, and then in `psql-header.vm` change to NULL and leave the change in `psql-footer` to be `NOT NULL`