Extend configuration server to reset password of different users

[mariusoe]

Currently, the configuration server provides an endpoint which can be used to change the password of the logged in user. Changing or resetting a password for different users is not possible. In case a user forgot its password, the administrator has to delete the user account and add it again with a new password.

In order to solve this problem and make the server more user-friendly, it should be able to reset the password of different users to some default or specific password (in case the required permissions are available - e.g. for administrators).