Add PDF Download endpoint

[jakejackson1]

Description

Add /download REST endpoint to download an entry's PDF document

Testing instructions

Screenshots

Checklist:

• I've tested the code.
• My code is easy to read, follow, and understand
• My code follows the accessibility standards.
• My code has proper inline documentation / docblocks.

Additional Comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.30%. Comparing base (141c78b) to head (aba940a).
Report is 1 commits behind head on development.

Additional details and impacted files

@@               Coverage Diff                @@
##           development    #1568       +/-   ##
================================================
+ Coverage        77.83%   93.30%   +15.47%     
================================================
  Files              252       57      -195     
  Lines            13920     1464    -12456     
  Branches           370      370               
================================================
- Hits             10834     1366     -9468     
+ Misses            3078       90     -2988     
  Partials             8        8               

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