register_new_matrix_user
Used to register new users with a given home server when registration has been disabled.
TLDR
Create a user interactively
$ register_new_matrix_user --config [path/to/homeserver.yaml]
Create an admin user interactively
$ register_new_matrix_user --config [path/to/homeserver.yaml] --admin
Create an admin user non-interactively (not recommended)
$ register_new_matrix_user --config [path/to/homeserver.yaml] --user [username] --password [password] --admin