Add jitter and exponential backoff when erroring

[robdefeo]

Is your feature request related to a problem? Please describe.
When cmd/indexer errors it does so without delaying, this can in itself cause other errors on the downstream system.

Describe the solution you'd like

• after each error wait an increasing amount of time
• add jitter
• Use library https://github.com/cenkalti/backoff

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered. Remove if not applicable

Additional context
Add any other context or screenshots about the feature request here. Remove if not applicable

[stale]

This issue has been automatically marked as stale because it has not had recent activity. The resources of the Mailchain team are limited, and so we are asking for your help. If this is a bug and you can still reproduce this error on the master branch, please reply in order to keep the issue open. If this is a feature request, and you feel that it is still relevant and valuable, please reply in order to keep the issue open. This issue will automatically be closed in the near future if no further activity occurs. Thank you for all your contributions.