open fun rxInsertUser(username: String, password: String, roles: MutableList<String>, permissions: MutableList<String>): Single<String>
Insert a new user into mongo in the convenient way
username - the username to be set
password - the passsword in clear text, will be adapted following the definitions of the defined io.vertx.reactivex.ext.auth.mongo.HashStrategy
roles - a list of roles to be set
permissions - a list of permissions to be set
Return