Update comments app

Add transaction handling. Add comment view link. Update views to
user ExternalObjectMixin. Add event tests.

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

mayan/apps/document_comments/tests/mixins.py

@@ -0,0 +1,26 @@
+from __future__ import unicode_literals
+
+from .literals import TEST_COMMENT_TEXT
+
+
+class DocumentCommentTestMixin(object):
+    def _create_test_comment(self):
+        self.test_document_comment = self.test_document.comments.create(
+            comment=TEST_COMMENT_TEXT, user=self._test_case_user
+        )
+
+
+class DocumentCommentViewTestMixin(object):
+    def _request_test_comment_create_view(self):
+        return self.post(
+            viewname='comments:comment_add', kwargs={
+                'pk': self.test_document.pk
+            }, data={'comment': TEST_COMMENT_TEXT}
+        )
+
+    def _request_test_comment_delete_view(self):
+        return self.post(
+            viewname='comments:comment_delete', kwargs={
+                'pk': self.test_document_comment.pk
+            },
+        )