suggest to add more tests for json serializer

[jhpoelen]

In trying to figure out how GBIF determines whether records have changed, I stumbled across

crawler/crawler-cli/src/test/java/org/gbif/crawler/dwca/fragmenter/StarRecordSerializerTest.java

Line 18 in 31da429

Archive archive1 = DwcaTestUtil.openArchive("/dwca/dwca-one-hundred-good-triplets-good-ids.zip");

Given that the existing change detection method uses json serialization in combination with an md5 hash to determine a change, I would suggest to add some test cases that take previously serialized json fragments and compare them to newly serialized json from a dwca. This would check that the underlying json serializer produces json in a consistent way. This would avoid a situation where all gbif records need updating whenever the the json serializer is updated with a change in serialization behavior.