Customer PDF controllers resolved the target document by raw mailable_id,
ignoring mailable_type, and skipped the expiry check on the JSON endpoints.
- Resolve via the $emailLog->mailable morph relation and assert the expected
type (abort 404) so a token issued for one document type can't disclose
another whose numeric id collides.
- Enforce isExpired() (abort 403) on every public path, including the JSON
getInvoice/getEstimate/getPayment endpoints.
- Harden EmailLog::isExpired() to treat a null/unresolvable mailable as
expired instead of throwing.
Adds tests for cross-type 404, JSON-path expiry 403, and the valid path.
