Fix 500 error when user has no data access token

[Annu881]

• Modified getDataAccessToken to check if token list is empty before accessing elements.
• If the list is empty, create a new token is created instead of throwing an IndexOutOfBoundsException
• Added test case testGetDataAccessTokenWhenNoTokensExist to verify correct behaviour when no token exist

Fixes #11905

Fix # (see https://help.github.com/en/articles/closing-issues-using-keywords)

Describe changes proposed in this pull request:

• Modified the getDataAccessToken(String username) method in UuidDataAccessTokenServiceImpl.java to check if the list of tokens is empty before accessing elements
• If the list is empty, the method now calls createDataAccessToken(username) to generate a new token
• Added comprehensive test case testGetDataAccessTokenWhenNoTokensExist to verify the fix handles the empty token list scenario correctly.

Checks

• [ x ] The commit log is comprehensible. It follows 7 rules of great commit messages. We can fix this during merge by using a squash+merge if necessary
• [ x ] Has tests or has a separate issue that describes the types of test that should be created. If no test is included it should explicitly be mentioned in the PR why there is no test.
• [ x ] Is this PR adding logic based on one or more clinical attributes? If yes, please make sure validation for this attribute is also present in the data validation / data loading layers (in backend repo) and documented in File-Formats Clinical data section!
• [ x ] Make sure your PR has one of the labels defined in https://github.com/cBioPortal/cbioportal/blob/master/.github/release-drafter.yml

Any screenshots or GIFs?

Not applicable - this is a backend bug fix with no UI changes.

Notify reviewers

@inodb @mavwolverine

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
75.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud