fix: head/get/delete/copy directory object should fail when corresponding file object exists

The API hanlders and backend were stripping trailing "/" in object
paths. So if an object exists and a request came in for head/get/delete/copy
for that same name but with a trailing "/" indicating request should
be for directory object, the "/" would be stripped and the request
would be handlied for the incorrect file object.

This fix adds in checks to handle the case with the training "/"
in the request.

Fixes #709

s3api/controllers/base.go

@@ -92,6 +92,10 @@ func (c S3ApiController) GetActions(ctx *fiber.Ctx) error {
 	if keyEnd != "" {
 		key = strings.Join([]string{key, keyEnd}, "/")
 	}
+	path := ctx.Path()
+	if path[len(path)-1:] == "/" && key[len(key)-1:] != "/" {
+		key = key + "/"
+	}
 
 	if ctx.Request().URI().QueryArgs().Has("tagging") {
 		err := auth.VerifyAccess(ctx.Context(), c.be, auth.AccessOptions{
@@ -2379,6 +2383,10 @@ func (c S3ApiController) DeleteActions(ctx *fiber.Ctx) error {
 	if keyEnd != "" {
 		key = strings.Join([]string{key, keyEnd}, "/")
 	}
+	path := ctx.Path()
+	if path[len(path)-1:] == "/" && key[len(key)-1:] != "/" {
+		key = key + "/"
+	}
 
 	if ctx.Request().URI().QueryArgs().Has("tagging") {
 		err := auth.VerifyAccess(ctx.Context(), c.be,
@@ -2577,6 +2585,10 @@ func (c S3ApiController) HeadObject(ctx *fiber.Ctx) error {
 	if keyEnd != "" {
 		key = strings.Join([]string{key, keyEnd}, "/")
 	}
+	path := ctx.Path()
+	if path[len(path)-1:] == "/" && key[len(key)-1:] != "/" {
+		key = key + "/"
+	}
 
 	var partNumber *int32
 	if ctx.Request().URI().QueryArgs().Has("partNumber") {