setup_user_2fa wrote each user's 2FA-setup instructions to the quoted
path "~$user/2fa-setup-instructions.txt". Tilde expansion does not occur
inside double quotes, so the path was treated literally and the write
failed with "No such file or directory", aborting the whole 2FA module
(and thus provisioning) under errexit.
Resolve the home directory explicitly with `getent passwd` and use that
absolute path for both the instructions file and the chown. Skip the
user cleanly if no home directory exists.
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mrcharles
b19bc87361