Use correct JSON schema dialect for param validation

[GfxKai]

Closes #13560

Whilst this issue is already closed, the problem is not actually fixed in v3, see #13560 (comment)

Context

This issue occurs when trying to deploy a flow which uses a Pydantic model as a parameter. Specifically, JSON schema validation for this parameter fails if the model contains a field with a numeric gt or lt constraint (or a type alias to that effect, e.g. pydantic.PositiveFloat).

Cause

1. On the client side, prefect.deployments.runner.RunnerDeployment calls prefect.utilities.callables.generate_parameter_schema to generate a JSON schema for the flow parameters

2. Internally, this calls prefect._internal.pydantic.v2_schema.create_v2_schema, which uses a subclass of pydantic.json_schema.GenerateJsonSchema for the actual schema generation

Crucially, this class (and Pydantic in general since since v2.0) uses Draft 2020-12 as the default JSON Schema dialect.

3. When Prefect server receives the POST /api/deployments/ request, FastAPI tries to construct and validate a prefect.server.schemas.actions.DeploymentCreate model from the request body

4. The model validation method for DeploymentCreate validates the parameter OpenAPI schema using prefect._internal.schemas.validators.validate_parameter_openapi_schema

5. Internally, this calls jsonschema.Draft4Validator.check_schema to do the actual validation

Obviously, this schema validation class uses the Draft 4 JSON Schema dialect.

As you can see in the JSON Schema docs, exclusiveMinimum and exclusiveMaximum were boolean as of Draft 4 but have subsequently changed to numeric type.

Proposed solution

Update the server-side validation to use jsonschema.Draft202012Validator

Checklist

• This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

[codspeed-hq]

CodSpeed Performance Report

Merging #15483 will not alter performance

_{Comparing GfxKai:patch-1 (acd7244) with main (3cdcf87)}

Summary

✅ 3 untouched benchmarks

[zzstoatzz]

thank you for the PR @GfxKai - nice catch!