feat(python): add Literal type support for const properties in Pydantic preset

[varundeepsaini]

Description

Add Literal type support for const properties in the Pydantic Python preset.

Previously, when a JSON Schema field was declared with the const keyword, the Pydantic preset generated a plain type:

class AnonymousSchema1(BaseModel): 
  country: str = Field()

Now it correctly generates a Literal type:

class AnonymousSchema1(BaseModel): 
  country: Literal["United States of America"] = Field(default='United States of America', frozen=True)

This implementation handles:

• String const values → Literal['value']
• Number const values → Literal[42]
• Boolean const values → Literal[True] / Literal[False]

Related Issue

Fixes #2225

Checklist

• The code follows the project's coding standards and is properly linted (npm run lint).
• Tests have been added or updated to cover the changes.
• Documentation has been updated to reflect the changes.
• All tests pass successfully locally. (npm run test).

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[coveralls]

Pull Request Test Coverage Report for Build 19969736921

Details

• 25 of 25 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 91.026%

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Totals
Change from base Build 19961633573:	0.007%
Covered Lines:	6943
Relevant Lines:	7420

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💛 - Coveralls

[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 SonarQube Cloud

[asyncapi-bot]

🎉 This PR is included in version 6.0.0-next.6 🎉

The release is available on:

• npm package (@next dist-tag)
• npm package (@next dist-tag)
• GitHub release

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