Complete with commit 8deb1f26f5a34a970e3c4046f0cc1fedbed460f1 (and fix with commit 3f9f3b2ed4db98de7c245cda1e06c4814805770f).
The following commands are offered by this new add-on:
'mongo setup' - Configures the project for MongoDB peristence.
'entity mongo' - Creates a domain type which can be backed by a MongoDB repository
'repository mongo' - Creates a Repository (interface & impl) for a given domain type.
Docs for layering support (and specifically mongo repositories) are coming.