unipdf dependency removal

[joagonca]

@ddvk To remove unipdf, we need to either remove the rmapi dependency, or refactor it.
I've looked into it and:

• Removing rmapi we would be bringing the code that parses v5 files into rmfakecloud.
• Refactoring rmapi, due to the thumbnail generation, we would need an external application (like pdftoppm from poppler-utils) to render it. At least I haven't found anything solid in native Go (or CGo).

Given that rmapi does a bit more than just the rendering - which is I think what is needed - what would be your considered approach for this?

I'm tending towards the removal of rmapi dependency of this project, and bringing in the code that parses v5, and using go-cairo to render the final PDF.

Thoughts?

[ddvk]

i'm for removing the rmapi dependency