Add prawn and prawn-svg to Gemfile for PDFs

What does this MR do and why?

Context

We want to use prawn and prawn-svg to build out PDF reporting features for our security features.

We previously built a proof of concept, and have decided to move forward implementing the report with prawn¹

Before beginning the development work, we need to:²

• get legal approval for the gem licenses ³
• adds the license approvals to the license scanner (!187297 (merged))
• update omnibus to with regards to the new gems (omnibus-gitlab!8249 (merged))
• update the gitlab project's Gemfile (this MR)

This MR

1. adds the gems to the gemfiles

References

• https://gitlab.com/gitlab-com/legal-and-compliance/-/issues/2565+
• Add license approvals for prawn pdf gems (!187297 - merged) • Michael Becker • 17.11
• Draft: Resolve "Build proof of concept for Proj... (!183327 - closed) • Michael Becker • 17.10

Screenshots or screen recordings

This MR only adds the dependencies. Below is a screen-recording from the proof of concept provided for context.

Proof of concept demo
demo We will be building out a version of this report going forward

How to set up and validate locally

1. With the branch pulled down, run bundle

   bundle

2. Verify the license check passes

   bundle exec license_finder

    # expected output
    ~/gdk/gitlab$ bundle exec license_finder
    LicenseFinder::Bundler: is active
    LicenseFinder::NPM: is active
    LicenseFinder::Yarn: is active
    LicenseFinder::Pipenv: is active
    
    All dependencies are approved for use

3. Verify hello world pdf can be generated

   # generates a hello.pdf file you should be able to open
   bundle exec rails runner "$(cat <<'EOT'
   require "prawn"
   
   Prawn::Document.generate("hello.pdf") do
     text "Hello World!"
   end
   EOT
   )"

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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related to: #524059 (closed)
Changelog: added

1. The proof of concept MR builds out a demo using the gems ↩

2. These steps come from the "Getting an Unknown Licensed Software Approved" and Legal's handbook page on "Using Open Souce Software" ↩

3. License approval was already obtained here ↩