Extra stage at the beginning named "Parse Source Schemas"?

[glen-84]

Copied from #130 (comment):

Should we add an extra stage at the beginning named "Parse Source Schemas", which parses the source schemas and may return INVALID_GRAPHQL? (it would replace 3.2.1.28 Invalid GraphQL)

I ask because from the "Validate Source Schemas" stage, you're usually working with already-parsed schemas.

The alternative is for the "Validate Source Schemas" stage to take the SDL and return the parsed schemas, but that seems less elegant, as it would be the only one of 4 validation stages that returns something.