Turn credentials generation (#102)

* abstract peer channel

* remove wip code

* refactor NewServer with Peer updates channel

* feature: add TURN credentials manager

* hmac logic

* example test function

* test: add TimeBasedAuthSecretsManager_GenerateCredentials  test

* test: make tests for now with hardcoded secret

* test: add TimeBasedAuthSecretsManager_SetupRefresh test

* test: add TimeBasedAuthSecretsManager_SetupRefresh test

* test: add TimeBasedAuthSecretsManager_CancelRefresh test

* feature: extract TURNConfig to the management config

* feature: return hash based TURN credentials only on initial sync

* feature: make TURN time based secret credentials optional

Co-authored-by: mlsmaycon <mlsmaycon@gmail.com>

management/server/config.go

@@ -1,5 +1,9 @@
 package server
 
+import (
+	"github.com/wiretrustee/wiretrustee/util"
+)
+
 type Protocol string
 
 const (
@@ -12,15 +16,23 @@ const (
 
 // Config of the Management service
 type Config struct {
-	Stuns  []*Host
-	Turns  []*Host
-	Signal *Host
+	Stuns      []*Host
+	TURNConfig *TURNConfig
+	Signal     *Host
 
 	Datadir string
 
 	HttpConfig *HttpServerConfig
 }
 
+// TURNConfig is a config of the TURNCredentialsManager
+type TURNConfig struct {
+	TimeBasedCredentials bool
+	CredentialsTTL       util.Duration
+	Secret               []byte
+	Turns                []*Host
+}
+
 // HttpServerConfig is a config of the HTTP Management service server
 type HttpServerConfig struct {
 	LetsEncryptDomain string