If a request to upload a file part to S3 fails for any 5xx reason it will begin using an exponential backoff to keep re-trying the upload until we've reached a minute of trying to access the endpoint.
This should resolve temporary resolution issues with URLs and certain S3 compatiable systems such as B2 that sometimes return a 5xx error and just need a retry to be successful.
Also supports using the server context to ensure backups are terminated when a server is deleted, and removes the http call without a timeout, replacing it with a 2 hour timeout to account for connections as slow as 10Mbps on a huge file upload.
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