Sending multiple links to a *-to-one association responds with 500 Internal Server Error

When sending multiple links to a one-to-one or many-to-one association, the server responds with 500 Internal server error due to the RepositoryPropertyReferenceController throwing an IllegalArgumentException (message: "Must send only 1 link to update a property reference that isn't a List or a Map."). Since a general IllegalArgumentException is thrown, this results in a HTTP 500 error from https://github.com/spring-projects/spring-data-rest/blob/aaadc344ab1bef4ed98cb0dbf6ca8ebd7c9262ff/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/RepositoryRestExceptionHandler.java#L88-L99.
Typically, the response for an error triggered by user input would be in the 4xx range, e.g. 400 Bad Request.
If a more specific exception was thrown, it could be handled by the ExceptionHandler to return a more correct HTTP error, and developers that integrate spring-data-rest can supply their own @ExceptionHandler to handle this error as well.