skolemize before writing files in postMultipart() and `putMultipart…

…()` (files require absolute URIs)

src/main/java/com/atomgraph/linkeddatahub/resource/graph/Item.java

@@ -282,6 +282,8 @@ public Response postMultipart(FormDataMultiPart multiPart, @QueryParam("default"
  final boolean existingGraph = getDatasetAccessor().containsModel(getURI().toString());
  if (!existingGraph) throw new NotFoundException("Named graph with URI <" + getURI() + "> not found");
 
+ new Skolemizer(getURI().toString()).apply(model); // skolemize before writing files (they require absolute URIs)
+
  int fileCount = writeFiles(model, getFileNameBodyPartMap(multiPart));
  if (log.isDebugEnabled()) log.debug("# of files uploaded: {} ", fileCount);
 
@@ -322,6 +324,8 @@ public Response putMultipart(FormDataMultiPart multiPart, @QueryParam("default")
  if (reader instanceof ValidatingModelProvider validatingModelProvider) model = validatingModelProvider.processRead(model);
  if (log.isDebugEnabled()) log.debug("POSTed Model size: {}", model.size());
 
+ new Skolemizer(getURI().toString()).apply(model); // skolemize before writing files (they require absolute URIs)
+
  int fileCount = writeFiles(model, getFileNameBodyPartMap(multiPart));
  if (log.isDebugEnabled()) log.debug("# of files uploaded: {} ", fileCount);