Add patch and tests for wrongly generated property names due to openapi-generator bug

[TimoGlastra]

OpenApi generator has a bug where property names are sanitized. This causes problems for some endpoints as they expect an @type property in the post object instead of an type property.

I have created an issue in the openapi-generator repo OpenAPITools/openapi-generator#4748, but I don't think it will be fixed in the near future.

For now I started with a patch that overwrites the wrong property names. https://github.com/ula-aca/aries-cloudagent-interface-javascript/blob/master/patches/api.patch. Whenever I come across an endpoint that has wrong generated property names I add it to the patch.

We should walk trough all endpoints, check if the property names are correct and add them to the patch if this is not the case. We should also write tests to somehow guarantee the patch is valid for the generated code, as the openapi schema can change.