fix: small fixes to the new import/export

[betodealmeida]

SUMMARY

This PR includes a few small fixes to the import/export feature:

1. Micro optimizations: some JSON fields may be empty strings, so we only serialize/deserialize them if they have an actual document.
2. Fixes: I was checking for the wrong exception when dumping JSON to a string (copy-and-paste mistakes, sigh).
3. Deserialize more fields: some of the fields that had a JSON payload were not being deserialized when exporting to YAML.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TEST PLAN

Unit tests green

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[hughhhh]

🚢