Access HAL+JSON-_compatible_ resources that have a custom media type using Traverson

I'm using Spring 5.1.8, Spring Boot 2.1.6, and Spring HATEOAS 0.25.1.

As an example, I want to access Spring Boot Actuator resources, which are transmitted with the media type application/vnd.spring-boot.actuator.v2+json.

For that to work, I have to provide a LinkDiscoverer for that media type:

    @Bean
    LinkDiscoverer actuatorLinkDiscoverer() {
        var halJsonPathTemplate = "$._links..['%s']..href"; // stolen from HalLinkDiscoverer
        return new JsonPathLinkDiscoverer(halJsonPathTemplate, parseMediaType(ActuatorMediaType.V2_JSON));
    }

The definition is basically a copy of HalLinkDiscoverer since I cannot create instances of that with a custom media type, or access the JSON Path template.

It would be nice if creating LinkDiscoverers for HAL+JSON-compatible media types were easier.

Start by reviewing Traverson, LinkDiscoverer, HalLinkDiscoverer, and JsonPathLinkDiscoverer, focusing on how media types and the JSON Path template are exposed. Define a less repetitive way to create LinkDiscoverers for HAL+JSON-compatible custom media types, and verify that Spring Boot Actuator resources can be accessed through Traverson.