fix: fixes the bucket/object tagging key/value name validation

Fixes #1579

S3 enforces a specific rule for validating bucket and object tag key/value names. This PR integrates the regexp pattern used by S3 for tag validation.
Official S3 documentation for tag validation rules: [AWS S3 Tag](https://docs.aws.amazon.com/AmazonS3/latest/API/API_control_Tag.html)

There are two types of tagging inputs for buckets and objects:

1. **On existing buckets/objects** — used in the `PutObjectTagging` and `PutBucketTagging` actions, where tags are provided in the request body.
2. **On object creation** — used in the `PutObject`, `CreateMultipartUpload`, and `CopyObject` actions, where tags are provided in the request headers and must be URL-encoded.

This implementation ensures correct validation for both types of tag inputs.

backend/common.go

@@ -317,14 +317,12 @@ func ParseObjectTags(tagging string) (map[string]string, error) {
 	return tagSet, nil
 }
 
-var validTagComponent = regexp.MustCompile(`^[a-zA-Z0-9:/_.\-+ ]+$`)
+// tag component (key/value) name rule regexp
+// https://docs.aws.amazon.com/AmazonS3/latest/API/API_control_Tag.html
+var validTagComponent = regexp.MustCompile(`^([\p{L}\p{Z}\p{N}_.:/=+\-@]*)$`)
 
-// isValidTagComponent matches strings which contain letters, decimal digits,
-// and special chars: '/', '_', '-', '+', '.', ' ' (space)
+// isValidTagComponent validates the tag component(key/value) name
 func isValidTagComponent(str string) bool {
-	if str == "" {
-		return true
-	}
 	return validTagComponent.Match([]byte(str))
 }