The idea is to have a server API to manage preferences, with flexible scope hierarchy.
A scope consists in a "type" (i.e.: global, user) and a "key" (i.e.: global, username).
A scope hierarchy consists in a scope order, used to find a preference value; when a value is searched, the first scope of this order to have the preference defined is used.

API details:

• First, a preferences storage service (PreferenceStorage) is responsible for plain I/O operations in a specific repository (preferences.git). To write (create/edit) a preference, a scope must be provided. To read (search) a preference(s), a scope or a scope resolution strategy must be provided.

• Second, a preferences store service (PreferenceStore) is responsible for providing a API to put, get, search and delete preferences, in a scoped manner.

• The scopes are totally flexible, but a default implementation (user and global scopes) will be provided by uberfire, if none is defined.