The fetcher only fetches by single date, not by date ranges

[galeone]

Being designed to fetch data from a single day, when we are fetching multiple days (think about a year or more!) we are executing AT LEAST N * k queries, where:

• N: is the number of user data we store for the day (e.g. sleep for that day)
• k: the number of days

At least, because for every (f *fetcher) user* method, we potentially run multiple queries (e.g. sub-activities, sleep stages, and all the other relationship).

This is not optimal and a better way to fetch the data should be designed