OpenApiComparer is not implemented

Hello,

My team is using this repository to generate our OpenAPI document, and we started using the OpenApiComparer recently in our project. This method returns a value so we believed it was working until recently when after making a change this still returned an empty list.

After looking at the implementation it's quite clear that this method does nothing but it is documented as being a method that "Compares two OpenApiDocuments and returns a list of differences.".

I believe this method should be removed or should throw instead.

After looking a bit more, there seems to be a valid implementation of this in the vnext branch that was never merged into master.

まず src/Microsoft.OpenApi/Services/OpenApiComparer.cs を読み、vnext ブランチにある有効な実装を調査します。意図された解決策が、メソッドを削除すること、例外をスローさせること、または vnext の実装を取り込むことのいずれであるかを判断します。完了の条件は、比較に対して OpenApiComparer が空の結果を黙って返さなくなることです。