Add setting migrations to apps

Add setting migrations for the common, converter, documents,
file metadata, and document signatures app.

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/file_metadata/setting_migrations.py

@@ -0,0 +1,15 @@
+from __future__ import unicode_literals
+
+from mayan.apps.common.serialization import yaml_load
+from mayan.apps.smart_settings.classes import NamespaceMigration
+
+
+class FileMetadataSettingMigration(NamespaceMigration):
+    """
+    From version 0001 to 0002 backend arguments are no longer quoted
+    but YAML valid too. Changed in version 3.3.
+    """
+    def file_metadata_drivers_arguments_0001(self, value):
+        return yaml_load(
+            stream=value or '{}',
+        )

mayan/apps/file_metadata/settings.py

@@ -5,8 +5,12 @@ from django.utils.translation import ugettext_lazy as _
 from mayan.apps.smart_settings.classes import Namespace
 
 from .literals import DEFAULT_EXIF_PATH
+from .setting_migrations import FileMetadataSettingMigration
 
-namespace = Namespace(label=_('File metadata'), name='file_metadata')
+namespace = Namespace(
+    label=_('File metadata'), migration_class=FileMetadataSettingMigration,
+    name='file_metadata', version='0002'
+)
 
 setting_auto_process = namespace.add_setting(
     global_name='FILE_METADATA_AUTO_PROCESS', default=True,