Add more logging to the upload_prep minifollowup

[GarethCabournDavies]

Standard information about the request

This is a user experience enhancement This change affects the offline search

This change follows style guidelines (See e.g. PEP8), has been proposed using the contribution guidelines

Motivation

During testing for (e.g. #4769), there isnt much about the progress of the upload_prep minifollowup - add it!

Contents

Adding logging lines

Testing performed

Code still runs, more logging produced

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