Add PDF support in attachment preview dialog

[w15eacre]

Add PDF support in attachment preview dialog

To preview the first page of a PDF file you need poppler >= 23.1.0.

Screenshots

Testing strategy

• Added tests for a new type of attachments. Unit tests were implemented to verify the functionality of the new attachment type.
• Manually. Performed manual testing to ensure the correct behavior of the new attachment feature in various scenarios.

Type of change

• ✅ New feature (change that adds functionality)

[w15eacre]

@droidmonkey Could you explain how to add these dependencies for the build?

[droidmonkey]

Will need to add it to the vcpkg.json and CMakeLists.txt, probably as an optional dependency

On the CI boxes we will install it

[w15eacre]

Great!
I figured out how to add a dependency and will do that this week. And I'll try adding UI tests because the dialog has become more complex.

[w15eacre]

@droidmonkey I couldn’t find qt5-image-formats-plugin-pdf in the package manager. Can I use Poppler instead?

[droidmonkey]

Poppler seems well regarded and supported, i don't have an issue with it.

[w15eacre]

@droidmonkey I need your help. The CI/CD environment doesn’t have the required library (Poppler). Do I need to add a new CMake option to enable or disable this feature?

[droidmonkey]

Don't worry about the CI env, I'll get it all set once your work is ready for review.

[w15eacre]

I have finished it. I think previewing the first page is enough, but there’s no problem with adding all pages to the preview.