"Only self" as a possible reportee type

## Description
We want to be able to let app owner define that an app is only available for the logged in person as reportee, and thus preselect this for everyone who navigates to app.

## Considerations
- Should not manipulate Altinn cookies
- Is it an requirement that the reportee is unchanged once user returns back to the portal?

### Ops requirements
> Are there any requirements for monitoring? What is being built and what could go wrong?
> Are there any requirements related to backup?

## Acceptance criteria
> Describe criteria here (i.e. What is allowed/not allowed (negative tesing), validations, error messages and warnings etc.)
- [ ] User specified in upper right corner should always be self, regardless of who is logged into the portal.

## Specification tasks

- [ ] Development tasks are defined

## Development tasks
> Add tasks here

## Test
> Add test cases here as checkboxes that are being tested as part of the changes.

## Definition of done
Verify that this issue meets [DoD](https://confluence.brreg.no/display/T3KP/Definition+of+Done#DefinitionofDone-DoD%E2%80%93utvikling) (Only for project members) before closing.

- [ ] Documentation is updated (if relevant)
- [ ] Technical documentation (docs.altinn.studio)
- [ ] User documentation (altinn.github.io/docs)
- [ ] QA
- [ ] Manual test is complete (if relevant)
- [ ] Automated test is implemented (if relevant)
- [ ] All tasks in this userstory are closed (i.e. remaining tasks are moved to other user stories or marked obsolete)

No files, tests, or entry points are identified in the issue. First clarify the acceptance criteria, cookie and return-to-portal behavior, operational requirements, and development tasks with the project team. Done requires agreed criteria, implementation and testing tasks, QA, and relevant documentation updates.

Written by the indexing model from the issue text.