zod type guard for @sendgrid/mail's ResponseError

zod-type-guard-sendgrid.ts

// NOTE: sendgrid doesn't properly export its ResponseError class, so this type
// (roughly) represents that type (with the type of body fixed)
const sendGridResponseErrorSchema = z.instanceof(Error).and(z.object({
    code: z.number(),
    response: z.object({
        headers: z.record(z.string(), z.string()),
        body: z.object({
            errors: z.array(z.unknown())
        })
    })
}));

type SendGridResponseError = z.infer<typeof sendGridResponseErrorSchema>;

function isSendGridResponseError(val: unknown): val is SendGridResponseError {
    return sendGridResponseErrorSchema.safeParse(val).success;
}