Some optional properties (of a Collection) are less optional than others

[algernon]

Some optional properties of a Collection, such as verification_link, description, and style_sheet seem to be included in the /api/collections/{alias} GET response, even if they're empty: they appear as "":

❯ curl -s "http://localhost:9080/api/collections/algernon" \
           -H "content-type: application/json" \
           -H "Authorization: Token ${TOKEN}" | jq .data.description
""

...while others, such as script, and signature do not appear in this, unless they're set. This makes it a tiny bit harder to implement serialization and deserialization for the Collection type, because I have to treat some of the optional properties more specially than the others.