Add support for workflow transition triggers.

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

mayan/apps/document_states/widgets.py

@@ -0,0 +1,13 @@
+from __future__ import unicode_literals
+
+from django.utils.html import format_html_join
+
+
+def widget_transition_events(transition):
+    return format_html_join(
+        sep='\n', format_string='<div class="">{}</div>', args_generator=(
+            (
+                transition_trigger.event_type.label,
+            ) for transition_trigger in transition.trigger_events.all()
+        )
+    )