Checks a request against API v2's request schemas (request_schemas.json, the schemas the API validates requests with) before it's sent, and says what the API would say about it. api_clients/validator_conformance checks that it agrees with the API.

Docspring.Connection adds it as a Tesla middleware (unless validate_requests: false), after the body is encoded as JSON. Each operation names itself in the request's opts (docspring_operation: "createSubmission"), and a request the API would reject returns {:error, %Docspring.ValidationError{}} without being sent.