fix(request-form): add handling for additional properties

[hamzamahmood]

What

This PR addresses an issue with the handling of additional properties in models that use [JsonExtensionData]. Specifically, it ensures that additional properties are flattened along with the model’s main members when data is sent as form data. Previously, the additional properties were being sent as a nested dictionary in form data, causing inconsistencies between the form data and the JSON body representation.

Why

Flattening the additional properties in form data ensures consistency between how data is represented in both the JSON body and form data formats. This alignment is important for APIs that process form data in a similar way to JSON payloads, ensuring the behavior is predictable and that consumers of the API receive a consistent structure. Additionally, this change improves compatibility with clients that expect all model properties, including those from [JsonExtensionData], to be at the top level.

Closes #80

Type of change

Select multiple if applicable.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause a breaking change)
• Tests (adds or updates tests)
• Documentation (adds or updates documentation)
• Refactor (style improvements, performance improvements, code refactoring)
• Revert (reverts a commit)
• CI/Build (adds or updates a script, change in external dependencies)

Testing

• Added unit tests to verify that models with additional properties, defined as both a property and a field, are correctly flattened when sent as form data.
• The tests include scenarios where:
  • Additional properties are included as part of a [JsonExtensionData] dictionary.
  • Form data correctly represents additional properties as flattened key-value pairs.
  • Consistency is maintained between the JSON body and form data outputs for models with [JsonExtensionData].
• These tests confirm that additional properties are no longer sent as nested dictionaries in form data.

Checklist

• My code follows the coding conventions
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added new unit tests

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
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