"content-type": "multipart/signed",
"content": [{"id": 2,
"content-type": "text/plain",
"content": "This is a test signed message.\n"},
{"id": 3,
"content-type": "application/pgp-signature",
"content-type": "multipart/signed",
"content": [{"id": 2,
"content-type": "text/plain",
"content": "This is a test signed message.\n"},
{"id": 3,
"content-type": "application/pgp-signature",