Upgrade FastAPI to the latest version by pinning it to >=0.110.0

[shangyian]

Summary

This PR takes the opportunity to upgrade DJ to the latest version of FastAPI. We're doing this because a number of updates to newer versions of FastAPI may fix the deadlock issue we were seeing with database sessions using Depends, namely this fix in 0.82.0:

🐛 Allow exit code for dependencies with yield to always execute, by removing capacity limiter for them, to e.g. allow closing DB connections without deadlocks.

This is preferable to rolling our own solution.

The primary changes in this PR are to accommodate the new starlette TestClient, which uses httpx rather than requests. There are also a few changes needed for the updated version of pydantic (although no breaking changes as we haven't upgraded to pydantic>=2).

Test Plan

Will update as tests are done.

• PR has an associated issue: #
• make check passes
• make test shows 100% unit test coverage

Deployment Plan

ASAP

[netlify]

✅ Deploy Preview for thriving-cassata-78ae72 canceled.

Name	Link
🔨 Latest commit	77102aa
🔍 Latest deploy log	https://app.netlify.com/sites/thriving-cassata-78ae72/deploys/65f8cb4c78880e00085d53ae

[agorajek]

I agree with your assessment @shangyian . Thanks for finding this in the FastAPI release notes!