Make the round participants sign the vtxo tree (#271)

* [proto] add APIs to send and receive musig2 signing data

* [common] add serialization functions for nonces and signatures

* [application] implements tree signing

* fix: remove old debug logs

* [proto] cleaning

* [common] fix musig2.go

* [application] fixes and logs

* [interface] fix: stop forwarding 2 times the events

* [client] add musig2 support + sign the tree when joining a round

* [interface] add new APIs into permissions.go

* [application][proto] rework PingResponse (return all events type)

* [common] split SetKeys into 2 distinct methods

* [client] fixes according to musig2.go changes

* [sdk] support tree signing + new PingResponse

* [sdk] fixes

* [application] revert event channel type

* [application] use domain.RoundEvent as lastEvent type

* [application] remove IsCovenantLess

* comments

* [application] revert roundAborted changes

* [interface] remove bitcointree dependencie

server/internal/core/application/covenantless_event.go

@@ -0,0 +1,43 @@
+/*
+* This package contains intermediary events that are used only by the covenantless version
+* they let to sign the congestion tree using musig2 algorithm
+* they are not included in domain because they don't mutate the Round state and should not be persisted
+ */
+package application
+
+import (
+	"bytes"
+	"encoding/hex"
+
+	"github.com/ark-network/ark/common/bitcointree"
+	"github.com/ark-network/ark/common/tree"
+	"github.com/decred/dcrd/dcrec/secp256k1/v4"
+)
+
+// signer should react to this event by generating a musig2 nonce for each transaction in the tree
+type RoundSigningStarted struct {
+	Id               string
+	UnsignedVtxoTree tree.CongestionTree
+	Cosigners        []*secp256k1.PublicKey
+}
+
+// signer should react to this event by partially signing the vtxo tree transactions
+// then, delete its ephemeral key
+type RoundSigningNoncesGenerated struct {
+	Id     string
+	Nonces bitcointree.TreeNonces // aggregated nonces
+}
+
+func (e RoundSigningNoncesGenerated) SerializeNonces() (string, error) {
+	var serialized bytes.Buffer
+
+	if err := e.Nonces.Encode(&serialized); err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(serialized.Bytes()), nil
+}
+
+// implement domain.RoundEvent interface
+func (r RoundSigningStarted) IsEvent()         {}
+func (r RoundSigningNoncesGenerated) IsEvent() {}