Description of changes

Closes #893

Summarize the changes made by this PR.

• Improvements & Bug fixes
  • Adds support for pydantic v2.0 by changing how Collection model inits - this simple change fixes pydantic v2
  • Fixes the cross version tests to handle pydantic specifically
  • Conditionally imports pydantic-settings based on what is available. In v2 BaseSettings was moved to a new package.
• New functionality
  • N/A

Test plan

Existing tests were run with the following configs

1. Fastapi < 0.100, Pydantic >= 2.0 - Unsupported as the fastapi dependencies will not allow it. They likely should, as pydantic.v1 imports would support this, but this is a downstream issue.
2. Fastapi >= 0.100, Pydantic >= 2.0, Supported via normal imports ✅ (Tested with fastapi==0.103.1, pydantic==2.3.0)
3. Fastapi < 0.100 Pydantic < 2.0, Supported via normal imports ✅ (Tested with fastapi==0.95.2, pydantic==1.9.2)
4. Fastapi >= 0.100, Pydantic < 2.0, Supported via normal imports ✅ (Tested with latest fastapi, pydantic==1.9.2)

• Tests pass locally with pytest for python, yarn test for js

Documentation Changes

None required.