Unified upload pipeline

[BurntimeX]

File uploads have been implemented differently several times in the software so far. The unified upload pipeline is intended to standardize these cases and make upload-relevant features available throughout:

• Chunked uploads
• Client-side image scaling
• Server-side image scaling
• User defined image processing (clipping, rotating, focal point for thumbnails, etc.)
• Thumbnail generation

ref https://www.woltlab.com/community/thread/278320-automatische-bildskalierung-auch-in-der-galerie/ https://www.woltlab.com/community/thread/266577-chunked-upload/ https://www.woltlab.com/community/thread/266059-titelbild-positionieren/ https://www.woltlab.com/community/thread/291287-%C3%BCberpr%C3%BCfung-der-erlaubten-dateiendung/