Add Thumbnail Support to the File Upload Component

[walldenfilippa]

Description

Thumbnail Support in File Upload Component
Patentstyret would like to add thumbnail support to the FileUpload component. We have created an initial implementation that provides the necessary foundation for displaying images or thumbnails within the component.
The current implementation focuses on the infrastructure required to support thumbnails. Thumbnail generation itself is not included and must be implemented by the TE. This is due to a combination of factors:

• Licensing considerations related to available NuGet packages, where some suitable alternatives are not open source.
• The need to align the implementation with the latest updates and architectural changes in the codebase.

Related PRs
Frontend: #3898
Backend: Altinn/app-lib-dotnet#1598
Storage: Altinn/altinn-storage#883 (merged)
App Local Test: Altinn/app-localtest#183
Documentation: Altinn/altinn-studio-docs#2602

Further Information About the Implementation

• Frontend - The frontend PR includes visual mockups/sketches demonstrating how thumbnails should be presented in the FileUpload component.
• Documentation - The documentation PR contains example code and implementation guidance for app developers who want to make use of the current thumbnail functionality.

Known Areas for Improvement

• Refactor and improve parts of the frontend implementation.
• Consider replacing the current hardcoded thumbnail data type ID with a configurable property on dataTypes.
• Improve backend caching and cache handling for thumbnail.

Additional Information

I have updated @ivarne and @framitdavid about this issue and the work completed so far. They will take over and continue working towards the final solution.