This is similar to https://jira.nypl.org/browse/SIMPLY-519 and inspired by similar user needs.

When you import an OPDS feed, you probably know the language of most of the works (they're probably all in the same language and it's probably English), even though the OPDS feed may not contain that information. It should be possible to configure a collection with a default language, so that books imported from the OPDS feed end up with (probably) the right language.