Use Active Storage for users profile picture

[viktorsmari]

• We also have the older user.avatar, for now

https://edgeguides.rubyonrails.org/active_storage_overview.html#linking-to-files

Issue

rails/rails#31228

• We have a routing issue, our catchall: match "*path", to: "errors#not_found", via: :all is blocking access to /rails/active_storage

If we remove the match.. then we won't get the following custom error anymore:

{
id: "not_found",
message: "Endpoint not found",
errors: null,
url: null
}

Instead we get rails default "No route matches" error.
Is that ok?