docs(upgrade_guide): update upgrade guide with Pydantic information

[leandrodamascena]

Issue number: #5249

Summary

Changes

In Powertools v3 we have dropped support for Pydantic v1 and are only supporting Pydantic v2 which is why we are no longer exporting pydantic types directly and allowing customers to import them directly from Pydantic.

1 - Pydantic V2 was a complete refactoring of the Pydantic project and they made several changes including, but not limited, to the way they export types, classes, methods, and others. If we continue to expose them directly from Powertools and some export in Pydantic has changed, our customers may get the impression that there is some bug in Powertools and that is not the experience we want to have for our customers.

2 - The way we were doing this was by exposing everything exposed from pydantic to our customers, but there is a long discussion in the Pydantic repository about how pydantic/pydantic#6748 when importing and loading things in this new version. We don't want our customers to inadvertently import everything from Pydantic and this could create some slowdown in their functions.

User experience

- #BEFORE - v2
- from aws_lambda_powertools.utilities.parser.pydantic import EmailStr

+ # NOW - v3
+ from pydantic import EmailStr

Checklist

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• Meet tenets criteria
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• PR title follows conventional commit semantics

Is this a breaking change?

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud