Add schema for drug device alerts

We should check that we want to actually use single-select here. After a discussion with @alicebartlett we decided single select currently requires no modification to go live (as multi select will require work to not collapse when using only 2 options) although we should consider the impact of using single selects on our finder endpoints.
This should be "about". As with the DSU schema it was in the wrong trello ticket, sorry :(