message: Expose constant Allow header
diff: "ConstantMetadataWriter:_headers_key": "Accept-Patch",
  "ConstantMetadataWriter:_headers_value": "application/sparql-update"
  },
  + {
  + "ConstantMetadataWriter:_headers_key": "Allow",
  + "ConstantMetadataWriter:_headers_value": "OPTIONS, HEAD, GET, PATCH, POST, PUT, DELETE"
  + },
  {
  "ConstantMetadataWriter:_headers_key": "MS-Author-Via",
  "ConstantMetadataWriter:_headers_value": "SPARQL"
  