Using database with hyphen
db = db.getSiblingDB("dbname-w-hyphen")
db.dropUser("admin")
Get user
use db
db.getUser("root")
Get all users
db.getCollection('system.users').find({})
Create user who can readWriteAnyDatabase
db.createUser({ user: "<username>", pwd: "<password>", roles: [ { db: "admin", role: "readWriteAnyDatabase" }] })