Add a retry mechanism when fetching email attachements

[whabanks]

Summary | Résumé

Adds retry capabilities when fetching email attachments during the send_to_providers process. Uses urllib3 retry functionality.

[jzbahrai]

thanks for adding this! I assumed we had a retry functionality piece already, but turns out we only have those for async celery tasks. would be good to take what you have done and make it a decorator at some point.

[whabanks]

thanks for adding this! I assumed we had a retry functionality piece already, but turns out we only have those for async celery tasks. would be good to take what you have done and make it a decorator at some point.

Love the decorator idea! I've added that to my misc. / downtime tasks list.