Implement logs model using Elasticsearch

- Implement logs model using Elasticsearch with tests
- Implement transition model using both elasticsearch and database model
- Add LOGS_MODEL configuration to choose which to use.

Co-authored-by: Sida Chen <sidchen@redhat.com>
Co-authored-by: Kenny Lee Sin Cheong <kenny.lee@redhat.com>

workers/test/test_exportactionlogsworker.py

@@ -12,6 +12,7 @@ from workers.exportactionlogsworker import ExportActionLogsWorker
 from test.fixtures import *
 
 
+# TODO(sidchen): Test logging to elastic search log model.
 @pytest.mark.parametrize('namespace,repo_name,expects_logs', [
   ('buynlarge', 'orgrepo', True),
   ('devtable', 'history', False),