#1304 - Update ref docs to properly show how to register custom media types.

Custom media types do NOT require registering a MediaTypeConfigurationProvider implementation with spring.factories. The reference docs must be updated to illustrate this. Also add to the javadocs so users are properly warned.

src/main/java/org/springframework/hateoas/config/MediaTypeConfigurationProvider.java

@@ -20,9 +20,12 @@ import java.util.Collection;
 import org.springframework.http.MediaType;
 
 /**
- * SPI to register a media type configuration provider.
+ * SPI used to register internal media types through spring.factories.
+ *
+ * WARNING: Do NOT implement this interface if you are coding a custom media type. See "Custom media type configuration" in the reference docs.
  *
  * @author Oliver Drotbohm
+ * @author Greg Turnquist
  * @see HypermediaMappingInformation
  */
 public interface MediaTypeConfigurationProvider {