Unable to set "Content-Type" header by @RequestHeader annotation

[PhillipMek]

Spring Boot 2.3.1
Spring Cloud OpenFeign 2.2.3
Java 11

Hi!
It looks like there is an issue introduced by change #314.

I have following method in my Feign client:

@PostMapping("/api/v2/topics/{topicName}")
Response sendMessage(
            @PathVariable("topicName") String topicName,
            @RequestBody Message message,
            @RequestHeader(value = HttpHeaders.CONTENT_TYPE) String contentHeader);

So, here I'm able to set "Content-Type" header dynamically by passing contentHeader param and this works until Spring Cloud Hoxton.SR5. When I set "spring-cloud-dependencies" version to "Hoxton.SR5" my app start failed with exception:
org.springframework.util.InvalidMimeTypeException: Invalid mime type "{Content-Type}": does not contain '/'

Exception thrown from method org.springframework.cloud.openfeign.support.SpringMvcContract#isMultipartFormData because in the given example of Feign method we have placeholder instead of particular header value and code

MediaType.valueOf(type); // here type = "{Content-Type}"

failed with InvalidMimeTypeException.

[OlgaMaciaszek]

Thanks @PhillipMek Was able to reproduce it.

[OlgaMaciaszek]

@PhillipMek I have also tried running it against Hoxton.SR4, however, it still fails here, and that code was there before the changes you've linked. Can you provide a minimal, complete, verifiable example that works before Hoxton.SR5 and breaks after updating to this version?

[PhillipMek]

@OlgaMaciaszek I forgot to mention that before update to Hoxton.SR5 I used Hoxton.SR2 version, so it works fine on Hoxton.SR2.

[OlgaMaciaszek]

@PhillipMek have just checked on Hoxton.SR2 and am still getting feign.codec.EncodeException. I can work on it anyway, but if you are able to provide a demo where it works for you, it will be easier. Let me know if you are able to provide a sample.