Types: make created_at not null
Types: make created_at not null

None of the DB entries are null, the API is never null, ...

I think this was translated directly from the schema (which does have
`NULL` as an option).

We should change the schema too, but I want to move faster.

iFixit/pulldasher,iFixit/pulldasher,iFixit/pulldasher,iFixit/pulldasher