Incorrect value of the MediaType.APPLICATION_PROBLEM_JSON_UTF8

[jstanik]

spring-web: 5.2.0
The media type APPLICATION_PROBLEM_JSON_UTF8 has incorrect value application/problem;charset=UTF-8 instead of application/problem+json;charset=UTF-8 missing the +json part.

APPLICATION_PROBLEM_JSON_UTF8 = new MediaType("application", "problem", StandardCharsets.UTF_8);

This causes regression like:

org.springframework.http.converter.HttpMessageNotWritableException: No converter for [class fully.qualified.name.of.our.Exception] with preset Content-Type 'application/problem;charset=UTF-8'

[rstoyanchev]

Seems like a good candidate for 5.1.x. I've added a backport issue.

[jhoeller]

@rstoyanchev This seems to have been a side effect of #22340 in 5.2 only. No need for a backport.