Resolves: GREG-141

- Passport Country now displays two letter code after
   selection.
- A heading has been added for identity information.
- An error message is now displayed if the user inputs both national id
   and passport information.

Resolves: GREG-120

Page now also handles failing api requests when searching.

Resolves: GREG-134

- Combine the /invite and /invitelink endpoints into one
- Return error messages from the backend
- Handle errors in the frontend
- Lower number of queries ran when calling the userinfo endpoint

Styling now matches the figma sketches

- Create a new loginbox component. To be used as invitation login
  latter.
- Add a util function that creates the correct stylized institution abbrevation

If the user is neither a guest or a sponsor, generic text explaining
this is shown. If they are a guest, they are shown the data related to
them. If they are a sponsor, they are redirected to the /sponsor/ route.

Resolves: GREG-97

Code for guest routes moved to their own folder so that we don't need
multiple api calls.
Serializer class for roles has been simplified with methods for
validation of each field and a separate one used in invites without
requiring the person field.

Resolves: GREG-61

When choosing the Register new guest button, you are now sent to a new
page where you can search for existing guests to prevent creating
duplicates. The page also has a register new guest button that takes you
to the previous version of the page, now located at /register/new

A future commit will make the search field functional.

Issue: GREG-75

Issue: GREG-75