CloudEvents incompatiable with Spring-framework 7.x

HttpMessageFactory.createReaderFromMultimap と CloudEventHttpUtils.toReader から開始し、スタックトレースの失敗経路をたどって、Spring Framework 7 でメッセージの受信を再現します。CloudEventHttpMessageConverter を通じた HttpHeaders の処理を追跡します。完了条件は、メッセージの受信で IncompatibleClassChangeError が発生しなくなることです。

I know there is a similar issue up already about upgrading to Spring-boot 2.7.18 but this project has lagged so far behind now that you can't even launch it with using an up-to-date ecosystem since Spring Framework 7 introduced a breaking change:

HttpHeaders changes
The HttpHeaders API has been revisited in 7.0. This class no longer extends the MultiValueMap contract. Underlying servers treat headers more like a collection of pairs, and many map-like operations do not behave or perform well, because headers are case-insensitive in the first place. We therefore removed several methods as a result and introduced fallbacks as immediately @Deprecated, like HttpHeaders#asMultiValueMap. Please consider other methods as much as possible. See #33913 for more details.

Stacktrace you get when running latest release of cloudevent and you try to receive a message:
"Class org.springframework.http.HttpHeaders does not implement the requested interface java.util.Map","error.stack_trace":"java.lang.IncompatibleClassChangeError: Class org.springframework.http.HttpHeaders does not implement the requested interface java.util.Map\n\tat io.cloudevents.http.HttpMessageFactory.lambda$createReaderFromMultimap$5(HttpMessageFactory.java:112)\n\tat io.cloudevents.http.HttpMessageFactory.createReader(HttpMessageFactory.java:70)\n\tat io.cloudevents.http.HttpMessageFactory.createReaderFromMultimap(HttpMessageFactory.java:114)\n\tat io.cloudevents.spring.http.CloudEventHttpUtils.toReader(CloudEventHttpUtils.java:55)\n\tat io.cloudevents.spring.mvc.CloudEventHttpMessageConverter.readInternal(CloudEventHttpMessageConverter.java:54)\n\tat io.cloudevents.spring.mvc.CloudEventHttpMessageConverter.readInternal(CloudEventHttpMessageConverter.java:39)\n\tat org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:196)\n\tat