Make sure patch requests sets the correct `language` param

[bjosttveit]

Description

Added a new method called getDataModelUrl instead of using getDataElementUrl for stateful apps. The difference being that the former has the includeRowIds and the latter has language as before. The reason for not including the language in the data model urls is that we store the url in formDataWrite to be able to check in tanstack whether or not we are currently saving, and we do not want the language to be included in the cache key. The current language is now therefore added only right before the patch request gets sent. I added a utility function for adding the query-parameter in a way where it does not matter if it already has any parameters set, to avoid checking if ? or & should be used etc.

Related Issue(s)

• closes #2037

Verification/QA

• Manual functionality testing
  • [x] I have tested these changes manually
  • [ ] Creator of the original issue (or service owner) has been contacted for manual testing (or will be contacted when released in alpha)
  • [ ] No testing done/necessary
• Automated tests
  • [x] Unit test(s) have been added/updated
  • [ ] Cypress E2E test(s) have been added/updated
  • [ ] No automatic tests are needed here (no functional changes/additions)
  • [ ] I want someone to help me make some tests
• UU/WCAG (follow these guidelines until we have our own)
  • [ ] I have tested with a screen reader/keyboard navigation/automated wcag validator
  • [x] No testing done/necessary (no DOM/visual changes)
  • [ ] I want someone to help me perform accessibility testing
• User documentation @ altinn-studio-docs
  • [ ] Has been added/updated
  • [x] No functionality has been changed/added, so no documentation is needed
  • [ ] I will do that later/have created an issue
• Support in Altinn Studio
  • [ ] Issue(s) created for support in Studio
  • [x] This change/feature does not require any changes to Altinn Studio
• Sprint board
  • [x] The original issue (or this PR itself) has been added to the Team Apps project and to the current sprint board
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• Labels
  • [x] I have added a kind/* label to this PR for proper release notes grouping
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[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
93.8% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud