fix(op): check if getTokenIDAndClaims succeeded

[muhlemmer]

When getTokenIDAndClaims didn't succeed,
so ok would be false.
This was ignored and the accessTokenClaims.Claims call would panic.

Closes #316

Definition of Ready

• I am happy with the code
• Short description of the feature/issue is added in the pr description
• PR is linked to the corresponding user story
• Acceptance criteria are met
• All open todos and follow ups are defined in a new ticket and justified
• Deviations from the acceptance criteria and design are agreed with the PO and documented.
• No debug or dead code
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• Critical parts are tested automatically
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[codecov]

Codecov Report

Merging #429 (645aa19) into main (45582b6) will decrease coverage by 0.02%.
Report is 1 commits behind head on main.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #429      +/-   ##
==========================================
- Coverage   52.69%   52.68%   -0.02%     
==========================================
  Files          74       74              
  Lines        5725     5727       +2     
==========================================
  Hits         3017     3017              
- Misses       2446     2447       +1     
- Partials      262      263       +1     

Files Changed	Coverage Δ
pkg/op/token_exchange.go	51.29% <0.00%> (-0.45%)	⬇️

[github-actions]

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