add client ID for plugin service

internal/util/auth/key.go

@@ -0,0 +1,22 @@
+package auth
+
+import (
+	"context"
+)
+
+type idKey struct{}
+
+type ID string
+
+var (
+	clientIDKey = &idKey{}
+)
+
+func ContextWithID(ctx context.Context, id ID) context.Context {
+	return context.WithValue(ctx, clientIDKey, id)
+}
+
+func IDFromContext(ctx context.Context) ID {
+	v, _ := ctx.Value(clientIDKey).(ID)
+	return v
+}