Page now also handles failing api requests when searching.

Resolves: GREG-134

Dates can now be changed after they have started and ended. This means
that there is no situation which needs disabling the input fields, and
disabling has been removed.

Start and end date can now be in the past. The following rules apply:
 - Start dates can be any date in the past, and no more into the future
   than the max days property of the role type.
 - End dates follow the same rules
 - End dates must be equal to or later than start date.

Notification publishing has been reviewed to ensure duplicate
notifications are not created when start or end date is today.

Resolve: GREG-148

- 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

Aria did not match label when changing langauge, and an id was
duplicated

All A and AA problems have been fixed except a missing label on an input
field.

Instead of forcing a reload of the page, we trigger a new api call in
the background, meaning we don't get a flash when verifying an identity.