Finalise Vuetify app as SPA

We want to turn AlekSIS frontend into an SPA finally. To do so, we need to find a way to still incorporate legacy views.

The rough plan is:

• Turn the Vuetify base template into a Vuetify component that is used as base component for all views
• Remove all decorations and the whole outer UI from the Materialize base template
• Implement menu generation in Vue, based on the routes in Vue router
• Make a generic component that loads legacy fragments from Django and renders them in an iframe
  • This requires correct handling of URL routes on both sides

TODOS:

• Routes with permissions (@yuha)
• Page Title/Favicon
• fix Sidenav Search
• Browser Titles
• fix highlighting in sidenav
• Vue Router 404
• Custom Footer Menu
• Fix iframe viewport size/breaking points
• make SPA reload user-related information as soon as login happens
• Language form in sidenav
• basic SW fixes
• Include routes from apps
• Include messages from apps
• end Impersonation in account menu
• introduce handling of failing queries due to network issues
• Additional rules for views
• Tests
  • Test with Alsijil: Messages, Course book (@yuha)
  • Test Sentry integration
  • Test Docker build
  • Test regular deployment steps and update handbook
  • Test dev environment setup steps and update handbook
• Nicer 404
• Check translations (en and de, @hansegucker)
• Test progress page (@hansegucker)
• change whoAmI resolver (DummyPerson when admin and no Person)/change handling of null whoAmI response (@yuha)
• anonymous user graphQL errors and faulty message when not logged in
• faulty login URLs
• Importing of messages does not work for vite production mode (since imports directories resulting from virtual modules are not evaluated properly in messages.js)
• reconsider handling of graphql errors when network connection is lost (ping query?) (@yuha)
• show user if offline (@yuha)
• Find and define a clean way to set page titles in components
• Refetch/Invalidate all querys (like whoAmI etc.) on login/logout/impersonate (@yuha)
  • Purge Apollo cache completely!
• Admin has Login- and SignUp-Button, despite being logged in or having signup disabled, due to reliance on permissions/rules only (the permission check for an admin is always true)
• External links are opened within iframe
• Factor out local GraphQL definitions into separate file
• Factor out Apollo configuration, utility code, etc. into separate files
• Most important encapsulations:
  • Everything that is specific to legacy pages is in LegacyBaseComponent
  • All utility code offered to components is in the AleksisVue plugin
  • Can we get rid of window.app?
• Pass GraphQL endpoint from Django
• Fix query importing (do not use require, maybe do not use ApolloQuery too much)
• Person page without data given (e. g. when offline & data not cached) is completely empty without any information
• add revisioning to additional precache paths
• Fix type errors in SideNav
• Fix type error in Additional Image (if person.secondaryImageUrl passed from PersonOverview is null)