Reuse TemplateList to display move-to options

This is slightly less efficient than getting the folder dicts from
"get_user_template_folders" directly, since:

- TemplateList returns both templates and folders.
- TemplateList encapsulates the dicts in model classes.

We'll compensate for this later on:

- We'll introduce a new caching approach to make the call fast.
- We'll expose a property to avoid the "if" in the comprehension.

app/models/template_list.py

@@ -157,6 +157,7 @@ class TemplateListFolder(TemplateListItem):
         service_id,
     ):
         super().__init__(folder, ancestors)
+        self.folder = folder
         self.service_id = service_id
         self.number_of_templates = len(templates)
         self.number_of_folders = len(folders)