Consider removal of deprecated elements as compatible

I'm using openapi-diff quite successfully to avoid accidental changes in the API (and therefore introducing a breaking change). We use it as a part of our pipeline.

The current struggle is: that sometimes one wants to introduce a breaking change (like the removal of obsolete API).
My initial idea would float around a two-step process:

• marking an element ad deprecated (keeping compatibility)
• removing the deprecated element

To do that, when processing the list of ChangedOpenApi#getChangedElements I'd need to know if the particular element is deprecatable and decide if the change is incompatible or not.

That looks to me like another SPI but I'm not sure if it's the direction. I know it's currently not possible and I'm not even sure if the direction of my thought even makes sense.

Start by examining ChangedOpenApi#getChangedElements and how openapi-diff currently classifies removals as incompatible. Review the existing extension points and the issue's proposed SPI idea before deciding on an approach. Done should provide a clear way to treat removal of deprecated elements as compatible while preserving the existing breaking-change checks.