[hw-8] add: comment service

comments/infra/grpc/middleware/validate.go

@@ -0,0 +1,18 @@
+package mw
+
+import (
+	"context"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+func Validate(ctx context.Context, req any, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {
+	if v, ok := req.(interface{ Validate() error }); ok {
+		if err := v.Validate(); err != nil {
+			return nil, status.Error(codes.InvalidArgument, err.Error())
+		}
+	}
+	return handler(ctx, req)
+}