Fix PDF XDG handler and add a new handler for JPG and PNG images

[nesteroff]

Description of changes

• Fixes the PDF XDG handler and moves common parts to a module.
• Adds another handler for JPG and PNG images.
• Enables XDG handlers in the comms-vm and gui-vm.
• Adds a simple image viewer to the zatura-vm.
• The file explorer can now open PDF files and images in zatura-vm.

Fixes SSRCSP-5360 and SSRCSP-5310.

Checklist for things done

• [x] Summary of the proposed changes in the PR description
• [x] More detailed description in the commit message(s)
• [x] Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
• [x] Contribution guidelines followed
• [ ] Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• [x] PR linked to architecture documentation and requirement(s) (ticket id)
• [x] Test procedure described (or includes tests). Select one or more:
  • [x] Tested on Lenovo X1 x86_64
  • [ ] Tested on Jetson Orin NX or AGX aarch64
  • [ ] Tested on Polarfire riscv64
• [ ] Author has run make-checks and it passes
• [ ] All automatic Github Action checks pass - see actions
• [ ] Author has added reviewers and removed PR draft status
• [ ] Change requires full re-installation
• [x] Change can be updated with nixos-rebuild ... switch

Instructions for Testing

Test opening PDF and image files in AppVMs, and in the GUIVM from the File Explorer.

[milva-unikie]

Tested on Lenovo-X1 (nixos-rebuild switch)

Issues:

• PDF files from Slack open in comms-vm browser. They should open to zathura like they do from the other vm:s.

Working:

• PDF files from Chromium, M365 services (in business-vm) and File Manager open in Zathura.
• JPG and PNG images from Chromium, M365 services (in business-vm), File Manager and Slack can be saved and opened in image viewer.
• Test-automation passes.

Other notes:

• File manager supports preview for JPG images. It would be cool to get the same support for PNG images in some future update (if that is possible).

[nesteroff]

• PDF files from Slack open in comms-vm browser. They should open to zathura like they do from the other vm:s.

Good catch. Should be fixed now.

• File manager supports preview for JPG images. It would be cool to get the same support for PNG images in some future update (if that is possible).

By default the file manager limits the size of files to show thumbnails to 2 MB. This can be change in the Edit > Preferences > Display menu.

[milva-unikie]

Tested on Lenovo-X1 (nixos-rebuild switch)

All is good now!

Working:

• PDF files from Chromium, M365 services (in business-vm), File Manager and Slack open in Zathura.
• JPG and PNG images from Chromium, M365 services (in business-vm), File Manager and Slack can be saved and opened in image viewer.
• Test-automation passes.

Notes:

By default the file manager limits the size of files to show thumbnails to 2 MB. This can be change in the Edit > Preferences > Display menu.

Thanks for correcting me. I was using too small sample size to draw conclusions :)