fix: rename 3_2_0.yaml to expected_3_2_0_upgraded.yaml and add upgrade test

[TristanSpeakEasy]

Summary

Fixes #128

The 3_2_0.yaml test file was incorrectly named - it contained an OpenAPI 3.1.0 document instead of a 3.2.0 document. This was confusing as the naming convention for other test files (e.g., 3_0_0.yaml, 3_1_0.yaml) uses the version number to indicate the source document's OpenAPI version.

Changes

1. Renamed and updated testdata file:

   • 3_2_0.yaml → expected_3_2_0_upgraded.yaml
   • Updated content to represent a valid 3.2.0 document after upgrade (transformed nullable, examples, exclusiveMinimum/Maximum)

2. Added test case to TestUpgrade_Success:

   • Tests upgrading from 3.1.0 to 3.2.0 with WithUpgradeTargetVersion("3.2.0") option
   • Verifies schema transformations: nullable → type array, example → examples, exclusiveMinimum/Maximum conversion

Schema Transformations Tested

Original (3.1.0)	Upgraded (3.2.0)
nullable: true on object	type: [object, "null"]
example: 123	examples: [123]
exclusiveMinimum: true + minimum: 0	exclusiveMinimum: 0
exclusiveMaximum: false + maximum: 100	maximum: 100
anyOf + nullable: true	adds { type: ["null"] } to anyOf

Testing

All upgrade tests pass including the new test case:

PASS openapi.TestUpgrade_Success/upgrade_3_1_0_to_3_2_0_yaml (0.03s)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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