Bug description

I'm having an issue with form data when using content type /. I managed to pinpoint it to this fix on Jackson Databind.
What happens now when initializing form data in DefaultServerWebExchange (code) is that JSON mappers also say they can read form data (here) and parsing therefore fails (because they can't).
Before this Jackson fix, ObjectMapper answered that it couldn't deserialize MultiValueMap.

Bug reproduce

Here is the simplest dummy app I've managed to build which replicates the issue: https://github.com/Dodomix/form-data-jackson-bug. The test fails with version 3.4.4 of Spring Boot, and passes with 3.4.3 (change in Jackson 2.18.2 -> 2.18.3). I'm opening the report here because the problematic code is in spring-web.

The exact behavior which changed in Jackson:

var objectMapper = new ObjectMapper();
objectMapper.canDeserialize(objectMapper.constructType(MultiValueMap.class));

Expected behavior

All tests pass.

System info

Java: Temurin 24