BUG: creating a user twice via the CLI should error obviously

[brassy-endomorph]

Describe the bug

To Reproduce

Do this:

aleph create user [email protected] -p abc123
aleph create user [email protected] -p def456

Expected behavior

There is an error of any sort, and the password is not altered.

Aleph version

3.15.3

[stchris]

The command create user is actually an UPSERT operation, so create user should fail if called on an existing user and we should have a proper update user command which does the above.