Rearrange and cover balance in subs mailer specs
Rearrange and cover balance in subs mailer specs

This moves them to a more unit-like style where the mailer methods are
the subjects. However, I did so only for the methods that show order
balance and thus we want to be extra sure of their coverage.

lin-d-hop/openfoodnetwork,openfoodfoundation/openfoodnetwork,lin-d-hop/openfoodnetwork,openfoodfoundation/openfoodnetwork,lin-d-hop/openfoodnetwork,mkllnk/openfoodnetwork,Matt-Yorkley/openfoodnetwork,lin-d-hop/openfoodnetwork,mkllnk/openfoodnetwork,openfoodfoundation/openfoodnetwork,mkllnk/openfoodnetwork,Matt-Yorkley/openfoodnetwork,mkllnk/openfoodnetwork,openfoodfoundation/openfoodnetwork,Matt-Yorkley/openfoodnetwork,Matt-Yorkley/openfoodnetwork