User: Refactoring authenticate
Include domain_name in the index (fix #120)
Support authentication & authorization over OAuth (fix #121)

Side effects:
 * Update docs
 * Update config
 * Allow specifying batch size in command line while indexing
 * pyelasticsearch's `_bulk` POSTs to the ES API root and this breaks
   authentication/authorization through Backstage. Consequently,
   the mapping and the indexing process had to be changed
Draft a new release, 0.13.4
Draft a new release, 0.13.5
Adapt base of unit tests to last changes
Removing dead code
TestDomain: Removed unused import
Support violations definitions per domain (Fix #100)
Config with i18n
Reviewer: Added tests for save_request()
Removing dead code
Fixed test_can_get_last_reviews_count_in_last_hour

Mocking datetime.utcnow()
Fixed integration tests

Missing search provider configs
Removing unused code