enable separate log levels for app, framework, canvasapi

[lsloan]

Problem

When LOG_LEVEL is set in .env, it applies to the Django framework as well as the application. That means when it is set to DEBUG, a ton of messages are logged by Django. At times, that can be useful. However, other times it's overwhelming and makes finding the app's debugging messages difficult.

Solutions

Establish another log level, perhaps DJANGO_LOG_LEVEL for setting Django's level and keep LOG_LEVEL just for this application.

Similarly, @ssciolla suggested canvasapi-specific log levels (see item № 1) in his code review of #11. Perhaps…

  'loggers': {
      'django': {
          'handlers': ['console'],
          'level': os.getenv('LOG_LEVEL', 'INFO').upper(),
          'propagate': False
      },
      'canvasapi': {
          'handlers': ['console'],
          'level': os.getenv('CANVAS_API_LOG_LEVEL', 'WARN').upper()
      }
  }