feat: adds Location in CompleteMultipartUpload response

Closes #1714

There is a `Location` field in the `CompleteMultipartUpload` result that represents the newly created object URL. This PR adds this property to the `CompleteMultipartUpload` response, generating it dynamically in either host-style or path-style format, depending on the gateway configuration.

s3api/controllers/base.go

@@ -31,12 +31,13 @@ import (
 )
 
 type S3ApiController struct {
-	be       backend.Backend
-	iam      auth.IAMService
-	logger   s3log.AuditLogger
-	evSender s3event.S3EventSender
-	mm       metrics.Manager
-	readonly bool
+	be            backend.Backend
+	iam           auth.IAMService
+	logger        s3log.AuditLogger
+	evSender      s3event.S3EventSender
+	mm            metrics.Manager
+	readonly      bool
+	virtualDomain string
 }
 
 const (
@@ -56,14 +57,15 @@ var (
 	xmlhdr = []byte(`<?xml version="1.0" encoding="UTF-8"?>` + "\n")
 )
 
-func New(be backend.Backend, iam auth.IAMService, logger s3log.AuditLogger, evs s3event.S3EventSender, mm metrics.Manager, readonly bool) S3ApiController {
+func New(be backend.Backend, iam auth.IAMService, logger s3log.AuditLogger, evs s3event.S3EventSender, mm metrics.Manager, readonly bool, virtualDomain string) S3ApiController {
 	return S3ApiController{
-		be:       be,
-		iam:      iam,
-		logger:   logger,
-		evSender: evs,
-		readonly: readonly,
-		mm:       mm,
+		be:            be,
+		iam:           iam,
+		logger:        logger,
+		evSender:      evs,
+		readonly:      readonly,
+		mm:            mm,
+		virtualDomain: virtualDomain,
 	}
 }
 

s3api/controllers/object-post.go

@@ -352,6 +352,10 @@ func (c S3ApiController) CompleteMultipartUpload(ctx *fiber.Ctx) (*Response, err
 			IfMatch:           ifMatch,
 			IfNoneMatch:       ifNoneMatch,
 		})
+	if err == nil {
+		objUrl := utils.GenerateObjectLocation(ctx, c.virtualDomain, bucket, key)
+		res.Location = &objUrl
+	}
 	return &Response{
 		Data: res,
 		Headers: map[string]*string{

s3api/controllers/object-post_test.go

@@ -536,7 +536,8 @@ func TestS3ApiController_CompleteMultipartUpload(t *testing.T) {
 			output: testOutput{
 				response: &Response{
 					Data: s3response.CompleteMultipartUploadResult{
-						ETag: &ETag,
+						ETag:     &ETag,
+						Location: utils.GetStringPtr("http://example.com/bucket/object"),
 					},
 					Headers: map[string]*string{
 						"x-amz-version-id": &versionId,