12582 wrong expired session message

[JamalAlabdullah]

Description

• Added an error code message GT_03to inform the user that the session is expired.
• Added test.

Related Issue(s)

• 12582

Verification

• [x] Your code builds clean without any errors or warnings
• [x] Manual testing done (required)
• [x] Relevant automated test added (if you find this hard, leave it and we'll help out)

Documentation

• [ ] User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.67%. Comparing base (468851f) to head (e7e4dd6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #12914 +/- ## ========================================== + Coverage 91.65% 91.67% +0.01% ========================================== Files 1410 1410 Lines 19987 19990 +3 Branches 2413 2413 ========================================== + Hits 18320 18325 +5 + Misses 1402 1400 -2 Partials 265 265 ```

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