Modify/add XMP metadata

[stefan6419846]

Explanation

We currently do not have an easy or documented way to add or modify XMP metadata. Thus we should evaluate if we need some new code or just some basic implementation.

Stack Overflow questions:

• https://stackoverflow.com/questions/466692/reading-writing-xmp-metadatas-on-pdf-files-through-pypdf
• https://stackoverflow.com/questions/79596480/add-xmp-dta-to-pdf-file-via-pypdf