This version introduces many breaking changes, but the old code gen
behaviour can be restored with the correct configuration.

However there is currently a bug, preventing us from completely switching
back to the old behaviour. The provided config should generate
equivalent code as soon as oapi-codegen/oapi-codegen#605
is released.

…d better error messages

The codegen does now correctly detect required attributes and fails if no id is present.
Ids are not required for `create` and set with the URL parameters for all other requsts.