This patch harmonizes the attribute names with what is used for `items`
and `checkouts` in terms of terminology.
It also adapts the tests so they are less random failure-prone (they had
a fixed value for the item type, which might make things explode if the
chosen value already exists on the DB.
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 78589dbe6e)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>