I have discovered some extractor tools which post results to metadata.jsonld, however the JSON that they post is not valid JSON-LD yet. We should use a JSON-LD library to validate that the submitted data is correct with respect to the standard. Any invalid JSON-LD should result in a response of 400 "Bad Request".

By adding this feature at the Clowder endpoint we will also ensure that those developing extractors will see the error when they run local tests with Docker. Hopefully we can find a validation kit that gives some details beyond "that JSON-LD is invalid".