Handle active sections better

[AlbertoPdRF]

With the way we currently handle active sections, it's really easy to forget to update the code to include new changes, so we should revisit how to handle them! This comes after #4423.

Possibilities:

• Add some sort of "navbar section" attribute to each of our controller (explanation)
• AFS website style (explanation)
• More?

This seems like another good first issue to me, so I'm labeling it as such!