Upgrade version of FastAPI and Pydantic

[laurent-laporte-pro]

Problem Statement

The version of FastAPI we are currently using is 0.73, released on 23 January 2022. Although this version is relatively recent, it should be noted that the library is undergoing rapid development within the open-source community.

This library has dependencies such as Pydantic, Starlette and Requests (used by Starlette). These dependencies also need to be updated to take advantage of new features, bug fixes and security patches.

However, we will not be able to upgrade to version 2 of Pydantic as this would require substantial changes to our code.

Since version 0.21 of Starlette, this library no longer has a dependency on Requests, having replaced it with Httpx, a more modern library. We need to adapt the source code of our application to take account of this change. What's more, given that we use Requests in a very limited and basic way, we can also abandon Requests in favour of Httpx without requiring any considerable effort.

We want to target the following versions:

• FastAPI: 0.103.1
• Httpx: 0.24.1
• Pydantic: 1.10.12
• Starlette: 0.27.0

and drop Requests.