add script to generate logins in project

[nvdk]

I think we can just add this script to the login service. Adding this as an issue so we don't lose track of it

[erikap]

@nvdk The semtech/registration-service already has a script to generate a user/account. Some improvements, like the automatic retrieval of MU_APPLICATION_SALT from the docker-compose.yml file, can be taken from the script you referenced, but probably better to open an issue on the registration service to track this.