add(auth): TokenEncoder interface parth of auth pkg

auth/auth.go

@@ -1,11 +1,6 @@
 package auth
 
 type (
-	Identifiable interface {
-		Identity() uint64
-		Valid() bool
-	}
-
 	Identity struct {
 		identity uint64
 	}

auth/interfaces.go

@@ -0,0 +1,12 @@
+package auth
+
+type (
+	Identifiable interface {
+		Identity() uint64
+		Valid() bool
+	}
+
+	TokenEncoder interface {
+		Encode(identity Identifiable) string
+	}
+)