chore: run go modernize tool

This is a fixup of the codebase using:
go run golang.org/x/tools/go/analysis/passes/modernize/cmd/modernize@latest -fix ./...

This has no bahvior changes, and only updates safe changes for
modern go features.

s3api/controllers/base.go

@@ -349,7 +349,7 @@ func ensureExposeMetaHeaders(ctx *fiber.Ctx) {
 
 	lowerExisting := map[string]struct{}{}
 	if existing != "" {
-		for _, part := range strings.Split(existing, ",") {
+		for part := range strings.SplitSeq(existing, ",") {
 			p := strings.ToLower(strings.TrimSpace(part))
 			if p != "" {
 				lowerExisting[p] = struct{}{}

s3api/middlewares/apply-default-cors.go

@@ -29,7 +29,7 @@ func ensureExposeETag(ctx *fiber.Ctx) {
 	}
 
 	lowerExisting := map[string]struct{}{}
-	for _, part := range strings.Split(existing, ",") {
+	for part := range strings.SplitSeq(existing, ",") {
 		p := strings.ToLower(strings.TrimSpace(part))
 		if p != "" {
 			lowerExisting[p] = struct{}{}

s3api/utils/utils.go

@@ -401,8 +401,8 @@ func ParseObjectAttributes(ctx *fiber.Ctx) (map[s3response.ObjectAttributes]stru
 			if len(value) == 0 {
 				break
 			}
-			oattrs := strings.Split(string(value), ",")
-			for _, a := range oattrs {
+			oattrs := strings.SplitSeq(string(value), ",")
+			for a := range oattrs {
 				attr := s3response.ObjectAttributes(a)
 				if !attr.IsValid() {
 					debuglogger.Logf("invalid object attribute: %v\n", attr)
@@ -500,16 +500,16 @@ type ChecksumValues map[types.ChecksumAlgorithm]string
 // e.g.
 // "x-amz-checksum-crc64nvme, x-amz-checksum-sha1"
 func (cv ChecksumValues) Headers() string {
-	result := ""
+	var result strings.Builder
 	isFirst := false
 
 	for key := range cv {
 		if !isFirst {
-			result += ", "
+			result.WriteString(", ")
 		}
-		result += fmt.Sprintf("x-amz-checksum-%v", strings.ToLower(string(key)))
+		result.WriteString(fmt.Sprintf("x-amz-checksum-%v", strings.ToLower(string(key))))
 	}
-	return result
+	return result.String()
 }
 
 // ParseCalculatedChecksumHeaders parses and validates x-amz-checksum-x header keys

s3api/utils/utils_test.go

@@ -992,7 +992,7 @@ func TestParseTagging(t *testing.T) {
 			},
 		}
 
-		for i := 0; i < lgth; i++ {
+		for range lgth {
 			res.TagSet.Tags = append(res.TagSet.Tags, s3response.Tag{
 				Key:   genRandStr(10),
 				Value: genRandStr(20),