SessionManager refactor

Review all the code that uses current_user information outside a react component and therefore needs to take information from SessionManager. If we get rid of these places then the implementation could be simplified by removing the SessionManager class

Basically review if we can access the user information only via redux state - if this is possible, then we could remove the `SessionManager` class, to avoid "duplication"

Start by locating the SessionManager class and every use of current_user outside React components, then compare those accesses with the Redux state. The work is done when user information can be accessed through Redux alone and the SessionManager class can be removed without losing required behavior.

Written by the indexing model from the issue text.