Add info option to print_to_pdf/2

[maltoe]

Now that we're calling Ghostscript from print_to_pdf/2 (optionally, for multiple sources), we may as well benefit from it.

• Make the embedding of metadata pieces a separate logic in Ghostscript*
  • While you're at it, refactor the GhostscriptWorker/Interface/Impl mess
• Move the info_option to pdf_option and add it as optional flag to print_to_pdf/2
  • Mention in the docs that this requires ghostscript
  • And writing the file to disk (mention this for the "join multiple sources" section as well)

[maltoe]

1. Split the postscript snippet (PDFA_def_ext.ps.eex or so)
2. Optionally render the postscript info snippet in the GhostscriptWorker.join/2 function
3. Render both snippets in GhostscriptWorker.convert/2

[ammancilla]

With the limited knowledge I have about the code base, I tried to come up with a (high level) plan about how to "smoothly" introduce a unified/smart print_to_pdf/3 that allows to print both pdf or pdfa files.

Implementation Details

Version ChromicPDF::API

• Add lib/chromic_pdf/api/v1/
  1. Add behaviour.ex specifying its behaviour
  2. Add impl.ex (or a better name if you can think of one) and move the code from ChromicPDF::API here.
  3. Update ChromicPDF::API to delegate function calls to ChromicPDF::API::V1::Impl

Add V2

The goal of the second version is to have a unified/smart print_to_pdf/3, capable to print both pdf and pdfa files based on the given function parameters. This version is also smart enough to know when to use Ghoshscript.

• Add lib/chromic_pdf/api/v2/

  1. Add behaviour.ex specifying its behaviour

  2. Add impl.ex (or a better name if you can think of one) and move the code from ChromicPDF::API here.

     How should a unified print_to_pdf looks like?

     The key is to have a well defined type for the opts that can be passed.

     For example:

     • any options related to pdfa files could be passed through a archival key.
     • any related to annotating a the file (author, title etc), could be passed through annotations key.
     • and so on ...

     The presence of one (or a combination) of the top level key of the opts map suffice to determine wether a pdf or
     a pdfa file should be printed and wether goshscript should be used or not.

  ```elixir
  @type opts :: {
       archival: map() | true,
       annotations: { title: atom() ... }
  }
  ```
  

  4. Update ChromicPDF::API to delegate function calls to ChromicPDF::API::V2::Impl.