Resolve "Allow admin to choose password on first login"

What does this MR do?

When the admin logs in with username: admin and any password for the first time, the user will be prompted to set a password. This password will be set and can from then on be used to login.

Does this MR meet the acceptance criteria?

• I have added tests to validate the new functionality.
• I have updated the documentation accordingly.
• I have added translations for all new client-side text.

closes #100 (closed)