fix: improper null checks on the CustomAuthenticationConverter

[m-gora]

Description

The CustomAuthenticationConverter performed typecasting before the null checks, which would result in a NullPointerException if the return value before the cast was null. To remedy this issue I refactored the code block to use a functional style Optional object, which automatically returns an empty Set of GrantedAuthorities if any of value in the json tree is null or the return value does not match the desired type of Map<String, Object>.

Note that this converter is used to perform the authentication. So fixing this bug is security relevant.

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files

[DominikPinsel]

@m-gora Great contribution :) It would be great if you could sign the Eclipse CLA with the same email, you did the commit with.

See also

• https://github.com/eclipse-tractusx/managed-identity-wallet/blob/main/CONTRIBUTING.md
• https://www.eclipse.org/legal/ECA.php

[m-gora]

Hi @DominikPinsel ,
I signed the agreement. Does the check rerun automatically once everything is in place?
I can't seem to force a rerun manually.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
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[DominikPinsel]

@borisrizov-zf Can you approve the workflow? :)

[borisrizov-zf]

@m-gora can you please rebase and change this to merge into develop.

Basic rebase workflow (if you want to use main in your form, you might have to enable force push for your fork):

git remote add upstream [email protected]:eclipse-tractusx/managed-identity-wallet.git
git remote fetch upstream
git checkout <your-branch>
git rebase upstream/develop
git push -f

[m-gora]

@borisrizov-zf

@m-gora can you please rebase and change this to merge into develop.

Basic rebase workflow (if you want to use main in your form, you might have to enable force push for your fork):

git remote add upstream [email protected]:eclipse-tractusx/managed-identity-wallet.git
git remote fetch upstream
git checkout <your-branch>
git rebase upstream/develop
git push -f

hmm, i did not see that there was a develop branch actually. it's probably easier to just close this PR and reopen rather than going through god-knows-how-many-commits and rebase.