The {usersInfo:...} command includes an `_id: 'username.dbname'` field for the document as stored in the local users collection.

The {rolesInfo:...} command does not since it was originally implemented to pull data from the RoleGraph which did not synthesize this data back in when serializing.

We should make a decision on whether these two two commands should be consistent and how. Options:

1. Leave them inconsistent.
2. Remove `_id` from {usersInfo:...} output as it is redundant.
3. Add an `_id` field to {rolesInfo:...} to gain consistency without breaking current callers of {usersInfo:...}