Bug: serialize Python request models with Swagger JSON property names

[daviburg]

Problem

The Python SDK correctly uses snake_case public model attributes, but ConnectorHttpClient.send_async serializes dataclass bodies using dataclasses.asdict. That emits Python attribute names instead of the JSON property names declared by the connector Swagger schema.

For example, a Swagger property printBackground is represented by Python print_background. asdict sends print_background, while the generated .NET model sends printBackground through JsonPropertyName. The connector service contract is the Swagger JSON name. Language-specific public naming must not alter the payload wire format.

Evidence

• PR Add new connectors (Phase 3) #54 adds generated request models with snake_case attributes.
• The shared Python HTTP client applies asdict before json.dumps.
• In the pinned PR Add new connectors (Phase 3) #54 snapshot, PDF.co request fields such as paper_size and print_background do not match Swagger paperSize and printBackground.
• Cross-language validation found 266 request-model serialization-key mismatches across the 12 connectors in PR Add new connectors (Phase 3) #54.
• This is a pre-existing shared runtime defect, not behavior introduced by PR Add new connectors (Phase 3) #54 binary-body changes.

Expected Fix

1. Preserve idiomatic Python snake_case public attributes and methods.
2. Generate or retain Swagger JSON property names as serialization metadata.
3. Replace bare asdict request serialization with a shared recursive wire serializer that emits Swagger property names for dataclasses, nested models, lists, maps, and additional_properties.
4. Preserve omitted None values and raw bytes request handling.

Regression Coverage

Add shared-runtime tests that capture the exact transport body for a snake_case property with a camelCase Swagger wire name, nested dataclasses and lists, additional_properties, omitted None values, and raw bytes. Add a generated-client contract test using PDF.co HtmlToPdfInput that verifies print_background emits printBackground and paper_size emits paperSize.

Related

• Python SDK PR Add new connectors (Phase 3) #54
• Trigger architecture issue Design: project x-ms-trigger routes as Connector Namespace callback contracts #59
• BPM generator PR 16445892