Resolve references in anyOf schema keys.

[joshtemple]

I found that the resolve_schema_references method doesn't expand JSON schema references in anyOf blocks. I added a new SchemaKey to make sure we recursively expand those $ref blocks.

Are there other keys we should also think about (e.g. allOf, oneOf)? Is there a more generalized approach used elsewhere in Singer for navigating the tree we should consider?

[KAllan357]

I think a better approach might be to figure out exactly how the RefResolver in jsonschema works.

In the meantime I think this change makes sense and we can continue to add additional support on an as needed basis.

[KAllan357]

Thanks 👍

[KAllan357]

Released in v5.4.1