Initial discord remote auth support.

It works, but nothing is persisted yet as the user object needs some tweaking
especially the database side.

remoteauth/clientpackets.go

@@ -0,0 +1,70 @@
+package remoteauth
+
+import (
+	"crypto/x509"
+	"encoding/base64"
+	"fmt"
+)
+
+type clientPacket interface {
+	send(client *Client) error
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Heartbeat
+///////////////////////////////////////////////////////////////////////////////
+type clientHeartbeat struct {
+	OP string `json:"op"`
+}
+
+func (h *clientHeartbeat) send(client *Client) error {
+	// make sure our op string is set
+	h.OP = "heartbeat"
+
+	client.heartbeats += 1
+	if client.heartbeats > 2 {
+		return fmt.Errorf("server failed to acknowledge our heartbeats")
+	}
+
+	return client.write(h)
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Init
+///////////////////////////////////////////////////////////////////////////////
+type clientInit struct {
+	OP               string `json:"op"`
+	EncodedPublicKey string `json:"encoded_public_key"`
+}
+
+func (i *clientInit) send(client *Client) error {
+	i.OP = "init"
+
+	pubkey := client.privateKey.Public()
+
+	raw, err := x509.MarshalPKIXPublicKey(pubkey)
+	if err != nil {
+		return err
+	}
+
+	i.EncodedPublicKey = base64.RawStdEncoding.EncodeToString(raw)
+
+	return client.write(i)
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// NonceProof
+///////////////////////////////////////////////////////////////////////////////
+type clientNonceProof struct {
+	OP    string `json:"op"`
+	Proof string `json:"proof"`
+}
+
+func (n *clientNonceProof) send(client *Client) error {
+	n.OP = "nonce_proof"
+
+	// All of the other work was taken care of by the server packet as it knows
+	// the payload.
+
+	return client.write(n)
+}