Unify Handling of allOf/anyOf and oneOf in Diff logic

まず SchemaDiff#resolveComposedSchema と SchemaDiff#addSchema を確認して allOf/anyOf がどのようにフラット化されるかを理解し、次に既存の oneOf 比較について ComposedSchemaDiffResult#diff と ChangedOneOfSchema を読みます。allOf/anyOf における構造の追加、削除、変更を、フラット化されたプロパティの変更と併せてどのように表現するかを定義します。diff が関連する詳細を失わずにコンポジションの変更を一貫して報告できれば完了です。

Current Behavior:

The diffing mechanism currently handles allOf/anyOf and oneOf differently within composed schemas:

1. allOf/anyOf: These schemas are recursively resolved and their properties are merged into the parent schema before the main diffing occurs. This happens in SchemaDiff#resolveComposedSchema, where properties from allOf/anyOf subschemas are added to the parent using SchemaDiff#addSchema. The original allOf/anyOf structure is effectively flattened.

2. oneOf: These schemas are not merged beforehand. Instead, the ComposedSchemaDiffResult#diff method performs a structural comparison of the oneOf lists between the old and new schemas. It identifies added, removed, or changed oneOf options, storing the results in a ChangedOneOfSchema object which is then attached to the ChangedSchema.

Suggested Behavior:

This difference in processing leads to an inconsistency. While the merging for allOf/anyOf simplifies property comparison later, it loses the structural information about changes within the allOf/anyOf lists. Conversely, oneOf retains this structural information because it's crucial for understanding changes in available options.

Consider unifying the approach. Perhaps allOf/anyOf could also be compared structurally, similar to oneOf, to provide a more consistent and potentially more informative diff result regarding the composition itself, rather than just the flattened outcome. This would allow tracking additions, removals, or modifications within allOf/anyOf lists directly.