Summary

Adds support for the x-ogen-name extension on OpenAPI parameters, allowing developers to customize the Go field name in generated parameter structs independently of the OpenAPI parameter name. This provides consistent naming control across schemas and parameters.

Fixes #1593

Changes

• Add XOgenName field to openapi.Parameter struct for storing custom names
• Parse and validate x-ogen-name extension in parameter parsing (must be valid exported Go identifier)
• Use x-ogen-name value when generating parameter struct field names
• Add positive test spec with path, query, and header parameter examples
• Add negative test specs for invalid/unexported identifiers
• Add integration test verifying custom parameter names work correctly

API Example

Before:

parameters:
  - name: pickuptype
    in: path
    schema:
      type: string

type MyOperationParams struct {
    Pickuptype string  // Auto-generated from "pickuptype"
}

After:

parameters:
  - name: pickuptype
    in: path
    x-ogen-name: CancelBy
    schema:
      type: string

type MyOperationParams struct {
    CancelBy string  // Uses custom x-ogen-name value
}

Testing

• Integration test validates custom names for path, query, and header parameters
• Parser tests verify invalid identifiers and unexported names are rejected
• Generated code compiles and type-checks correctly
• Mirrors existing x-ogen-name behavior for schemas