sign method
Create a signature of the body
with key
return the signature as bytes
Implementation
@override
Uint8List sign(JWTKey key, Uint8List body) {
assert(key is EdDSAPrivateKey, 'key must be a EdDSAPrivateKey');
final privateKey = key as EdDSAPrivateKey;
return ed.sign(privateKey.key, body);
}