TC: Add ndjson and request payload checking support to fake.json + update tests for tc.record

[skalish]

↪️ Pull Request

Relates to #423

💻 Examples

✔️ PR Todo

• [ ] Added/updated testing for this change
• [x] Included links to related issues/PRs
• [x] Update relevant docs + docstrings
• [ ] Update the CHANGELOG under the current -dev version:
  • Add changelog entries under any that apply: BREAKING CHANGES, NEW FEATURES, BUG FIXES.
  • Changelog entry format: [#<issue number>](<link to issue>) <change description>

[skalish]

Note: One more commit incoming with docstrings addressing the remaining comments.