[mongodb] Delete user from system collection if user database doesn't exist. Use it from mongoshell

mongo_drop_user_from_notexisteddb.js

var users = db.system.users.distinct("_id")
var dbs = db.getMongo().getDBNames()
users.forEach( function(uid) {
    var dbname = uid.split(".")[0]
    if (dbs.includes(dbname)) {
        print(dbname + " exist")
    } else {
        db.getMongo().getDB(dbname).dropUser("dev_user")
    }
})