Migrate jsonschema go library

[wagoodman]

Today we use github.com/alecthomas/jsonschema to generate our jsonschema, however, that repo has been moved to github.com/invopop/jsonschema. We should migrate to using the latest library, however, initial testing shows that the json schema is very different than the schemas generated in the past. We should check that these differences have no impact when replacing this library.