fix: switch to go-multicodec mappings (#240)

The mappings in go-cid were maintained by hand and are invalid.
More details in ipfs/go-cid#137

This is switching to go-multicodec which has correct mappings
that are generated, not written by hand.

Co-authored-by: Daniel Martí <mvdan@mvdan.cc>

core/peer/peer.go

@@ -9,6 +9,7 @@ import (
 	"github.com/ipfs/go-cid"
 	ic "github.com/libp2p/go-libp2p-core/crypto"
 	b58 "github.com/mr-tron/base58/base58"
+	mc "github.com/multiformats/go-multicodec"
 	mh "github.com/multiformats/go-multihash"
 )
 
@@ -162,13 +163,9 @@ func Encode(id ID) string {
 
 // FromCid converts a CID to a peer ID, if possible.
 func FromCid(c cid.Cid) (ID, error) {
-	ty := c.Type()
-	if ty != cid.Libp2pKey {
-		s := cid.CodecToStr[ty]
-		if s == "" {
-			s = fmt.Sprintf("[unknown multicodec %d]", ty)
-		}
-		return "", fmt.Errorf("can't convert CID of type %s to a peer ID", s)
+	code := mc.Code(c.Type())
+	if code != mc.Libp2pKey {
+		return "", fmt.Errorf("can't convert CID of type %q to a peer ID", code)
 	}
 	return ID(c.Hash()), nil
 }