required field collection missing in joplin collection for sqlalchemy

[philvarner]

The result Items from searching for the joplin collection do not have a collection attribute. Run: http://localhost:8081/search?collections=joplin

Per the STAC spec, defining the collection attribute in Item:

The id of the STAC Collection this Item references to (see collection relation type). This field is required if such a relation type is present and is not allowed otherwise. This field provides an easy way for a user to search for any Items that belong in a specified Collection. Must be a non-empty string.

Note that this works for pgstac.