Fix/scan levels

[Donnype]

Changes

Backend checks on current permissions setup for changing scan levels. This is the best I could do in a short time but could use a better setup (either mixins or using django permissions).

Issue ticket number and link

Popped up in #86.

Proof

One of the pages after removing an indemnification:

Checklist for author(s):

• This PR comes from a feature or hotfix branch, in line with our git branching strategy;
• I have squashed all commits before merging this PR;
• This PR is "bite-sized" and only focuses on a single issue, problem, or feature;
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• I have made corresponding changes to the documentation, if necessary;
• I have written unit, integration, and end-to-end tests for the change that I made;

## Checklist for functional reviewer(s):
- [ ] If a non-trivial PR: This PR is properly linked to an issue on the project board;
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- [ ] I have ran `make test-rf` and all end-to-end Robot Framework tests pass;
- [ ] I confirmed that the PR's advertised `feature` or `hotfix` works as intended;
- [ ] I confirmed that there are no unintended functional regressions in this branch;

### What works:
* _bullet point + screenshot (if useful) per tested functionality_

### What doesn't work:
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### Bug or feature?:
* _bullet point + screenshot (if useful) if it is unclear whether something is a bug or an intended feature._

## Checklist for code reviewer(s):
- [ ] The code passes the CI tests and linters;
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[underdarknl]

please create a new ticket for refactoring this into a method on the user or OOI model instead.