feat(mu): add retry mechanism for sendDataItem

[jfrain99]

Background

Currently in the MU, when a message is received, it runs sendDataItem, which initializes a task queue and pushes all subsequent messages. These worker thread messages have a retry mechanism and sqlite backup such that if an error were to occur during evaluation, it would retry and start again.

Problem

The MU post route, specifically sendDataItem, has no retry mechanism, and failures here (while rare) result in message loss.

Proposed Solution

Add a similar mechanism as the worker thread retry to the sendDataItem flow.

[jfrain99]

Closed by #1099