Initial commit to support staging file background image generation and caching.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/sources/storages.py

@@ -0,0 +1,18 @@
+from __future__ import unicode_literals
+
+import yaml
+
+from django.utils.module_loading import import_string
+
+from .settings import (
+    setting_staging_file_image_cache_storage,
+    setting_staging_file_image_cache_storage_arguments,
+)
+
+storage_staging_file_image_cache = import_string(
+    dotted_path=setting_staging_file_image_cache_storage.value
+)(
+    **yaml.safe_load(
+        setting_staging_file_image_cache_storage_arguments.value or '{}'
+    )
+)