feat(webdav): delete privacy header and optimize 302 (#2534)

* fix: delete set-cookie from sharepoint webdav response header

* fix: avoid two redirects when using webdav

* fix: return the correct Content-Type instead of just `application/octet-stream`

* feat: webdav backend localOnly -> proxyOnly

drivers/webdav/meta.go

@@ -16,7 +16,7 @@ type Addition struct {
 var config = driver.Config{
 	Name:        "WebDav",
 	LocalSort:   true,
-	OnlyLocal:   true,
+	OnlyProxy:   true,
 	DefaultRoot: "/",
 }