Add plugable locking backend support. Add threadsafe file lock backend.

mayan/apps/lock_manager/settings.py

@@ -1,9 +1,20 @@
 from __future__ import unicode_literals
 
-from django.conf import settings
+from django.utils.translation import ugettext_lazy as _
 
+from smart_settings import Namespace
+
+DEFAULT_BACKEND = 'lock_manager.backends.model_lock.ModelLock'
 DEFAULT_LOCK_TIMEOUT_VALUE = 30
 
-DEFAULT_LOCK_TIMEOUT = getattr(
-    settings, 'LOCK_MANAGER_DEFAULT_LOCK_TIMEOUT', DEFAULT_LOCK_TIMEOUT_VALUE
+namespace = Namespace(name='lock_manager', label=_('Lock manager'))
+
+setting_backend = namespace.add_setting(
+    default=DEFAULT_BACKEND,
+    global_name='LOCK_MANAGER_DEFAULT_BACKEND',
+)
+
+setting_default_lock_timeout = namespace.add_setting(
+    default=DEFAULT_LOCK_TIMEOUT_VALUE,
+    global_name='LOCK_MANAGER_DEFAULT_LOCK_TIMEOUT',
 )