7.0.3: Secure XML parsing

Small maintenance release to upgrade dependency to signature-api-specification-jaxb, which features a securely configured XML parser denying DOCTYPE declarations. This is not a critical update, since XML-parsing is only done on responses from the Posten signering API.

What's Changed

• Upgrade signature-api-specification by @runeflobakk in #320

Full Changelog: 7.0.2...7.0.3