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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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