Link projects of the glossary's organization to the glossary, so that
their translators get its terms. Linking adds each project's target
languages to the glossary. A project has at most one glossary.

The request is all or nothing: if any project can't be linked, none is.
It names any number of projects; a project named twice counts once.
A project that doesn't exist in the glossary's organization gets a
404, and an archived project, a project already linked to another
glossary, or one with a different source language than the glossary,
gets a 409; each error has a /data/{i} pointer to the project. If
any project doesn't exist, only the 404s are returned. To move a
project to this glossary, unlink it from the other one first. A project
already linked to this glossary is not an error, unless it's archived.

Only organization administrators can link projects, and only on a plan
that supports glossary upload.