Domain-verified Signatures with SvcSigMud chunks

Service Signature Mud is opaque, but holds a secure hash to validate the preceding range of chunks in this KIP Document.

As with SigMud, referenced content is not signed, but the references themselves are, possibly including secure hashes.

Since an interaction over the KIP Service is required, which may incur contacting a remote KIP Daemon, some privacy is built in with an added salt in the signature, but for a given document this is still fixed. Choose beforehand what realm you intend to trust with this; but mostly it will be the realm of a sender that you would be likely to trust if known.

Unlike the interaction for SvcKeyMud, this is a public operation, and no credentials are required. The KIP Service login is done with the SASL ANONYMOUS mechanism.

Code: Creation of a SvcSigMud uses the C-API format, and is simply

svcsigmud = SvcSigMud (b'\x2b...\xb2')

CBOR: The format in KIP Document for this chunk is simply an array with tag 9 for SvcSigMud and the binary content from the C-API:

[ 9, "\x2b..\xb2" ]