text: Title: Making django_db_blocker un-opt-outable is zealous and lame
  Body: Use of `django_db_blocker` to cripple use of the database outside of specially tagged tests and fixtures interferes with Django model `get_or_create` calls at import time, which is how some systems ensure the presence of fundamental data across environments.
  
  Making this behavior not configurable is disruptive and annoying. It results in the need to patch the patcher, a la 
  ```
  # settings/test.py
  from pytest_django import plugin
  plugin._blocking_manager = mock.MagicMock()
  ```
  
  Please consider a means to disable this behavior through settings.