Add error messages for `data/qualities/{id}`

[PGijsbers]

As detailed in #10

[Mahhheshh]

I think, I got this..

[PGijsbers]

The immediate issues were addressed by @Mahhheshh in #253. I'm leaving this issue open because there are some errors that currently do not occur because of the data in the test database. To test those code paths, we will need to update the test database (or manipulate it with queries inside a test).