config/test: Add `maintenancedb` section so db:setup works
config/test: Add `maintenancedb` section so db:setup works

The script `db:setup` requires settings for a maintenance database and
the test environment didn't have. This change fixes it making it
possible to run the following command:

  $ NODE_ENV=test npm run db:setup

The above command will attempt to create a user & then the application
database for a given environment.

OpenCollective/opencollective-api,OpenCollective/opencollective-api,OpenCollective/opencollective-api