Lack of symmetry for streaming media types in WebClient and on the server with MVC

JacksonJsonDecoder has a list of mime types including APPLICATION_NDJSON.
But the ReactiveTypeHandler (used on the server side) has WILDCARD_SUBTYPE_SUFFIXED_BY_NDJSON so it supports a wider range of media types. Ideally they would be the same.

A workaround is to just use application/x-ndjson on the server. Or to replace the default JSON decoder on the client side:

	@BeforeEach
	void setUp(@Autowired WebClient.Builder builder, @LocalServerPort int port) {
		this.rest = builder.codecs(config -> {
			MimeType[] mimeTypes = new MimeType[] {
					MediaType.APPLICATION_JSON,
					new MediaType("application", "*+json"),
					MediaType.APPLICATION_NDJSON,
					MediaType.valueOf("application/*+x-ndjson")
			};
			JacksonJsonDecoder decoder = new JacksonJsonDecoder(JsonMapper.builder(), mimeTypes);
			config.defaultCodecs().jacksonJsonDecoder(decoder);
		}).baseUrl("http://localhost:" + port).build();
	}

Start by comparing the supported media types in JacksonJsonDecoder with the WILDCARD_SUBTYPE_SUFFIXED_BY_NDJSON handling in ReactiveTypeHandler. Trace the existing WebClient and server-side MVC paths that use these classes, then check their related tests if present. Done means both sides accept the same relevant streaming JSON media types without requiring the workaround described in the issue.