Hide pages and/or cards depending on faculty

[bdmendes]

Since the new navbar/nav schema, the old page hide mechanism is now useless. Study factory/conditional rendering for faculty-specific data.

[limwa]

An API I thought for this was

FacultyFilter(
  faculties: ["feup", "fmup"],
  build: (context, authorizedFaculties) => FacultyMap(...)
)

There are a few aspects that I think make this proposal good:

• It promotes composability of widgets, that is, a widget doesn't need the faculty filter to work, but the faculty filter enhances it
• the listing of the faculties directly and not on a central widget allow developers to reason more easily about what is shown when a user is of a given faculty
• the build function prevents the initState function or the constructor of the FacultyMap widget being called unless the user is of a faculty that is on the list.
• the authorizedFaculties, the list of the faculties that are both in the user's faculty list and on the filter faculties, allows us to, inside the authorized widget, make decisions about what to show the user.
• We can have FacultyFilters inside other FacultyFilters and multiple FacultyFilter in the same page. We can also have FacultyFilters on the navbar.

The FacultyFilter would get the user's faculties from a provider.