Make CRON tasks more resilent

[alysivji]

As a developer, I want CRON jobs to be resilient.

Background

GitHub Summary CRON task is a CRON job that runs once per day... depending on how the Slack workspace has configured the application.

When this task fails with an error, a message is not posted for that workspace. Fortunately this does not happen unless there is an error from the Slack API.

Acceptance Criteria

• improve logging
  • what status code did we fail with?
  • add failure message to error log
• retry task until it succeeds
  • maybe post a message to the channel saying that we are experience problems with the Slack API
  • fortunately the task has been designed to take a datetime and calculate the summary using that reference point