idp: Create parent directories if they don't exist

The parent directories of the identifier-registration.yaml config file might
not exist when starting idp. So instead of creating just the top most
directory use MkdirAll to also create the parents.

changelog/unreleased/idp-parent-dir.md

@@ -0,0 +1,6 @@
+Bugfix: Create parent directories for idp configuration
+
+The parent directories of the identifier-registration.yaml config file might
+not exist when starting idp. Create them, when that is the case.
+
+https://github.com/owncloud/ocis/issues/2667

idp/pkg/service/v0/service.go

@@ -73,7 +73,7 @@ func createConfigsIfNotExist(assets http.FileSystem, filePath, ocisURL string) e
 
 	folder := path.Dir(filePath)
 	if _, err := os.Stat(folder); os.IsNotExist(err) {
-		if err := os.Mkdir(folder, 0700); err != nil {
+		if err := os.MkdirAll(folder, 0700); err != nil {
 			return err
 		}
 	}