Bump the Singer SDK requirement and use its JSON schema resolution helper

[edgarrmondragon]

Similar to https://github.com/reservoir-data/tap-neon/blob/9fa4096901c874cc82163f2014364b6ee68b8944/tap_neon/tap.py#L98, but we read the OpenAPI spec file for the API in question, and map the stream to a component schema, resolving any references.