Custom WebFlux encoders/decoders are placed below defaults

[gregturn]

When registering custom encoders and decoders to handle media types (e.g. application/hal+json) inside https://github.com/spring-projects/spring-hateoas/blob/master/src/main/java/org/springframework/hateoas/config/WebClientConfigurer.java, they are placed too far down to get read.

The default decoders includes a DecoderHttpMessageReader with mime types application/json and application/*+json.

application/json is okay, because that is quite specific. However, putting a pattern matcher for application/*+json ahead of application/hal+json causes the default one to always get selected. And this will happen for any other media type that registers a JSON-based media type (e.g. HAL-FORMS at application/prs.hal-forms+json).

I don't know if this means custom encoders and decoders should be moved to the front, or if something more sophisticated is needed, like putting wildcard-based patterns after non-wildcard-based ones.

For now, it forces us to disable the default registry just to get operational, which in turn causes headache for downstream projects like Spring Cloud Sleuth that are having their own WebClient post processing trounced by Spring HATEAOS.