partial load usage data

[s-sajid-ali]

#73 loads all usage data via plotly htmls but that's slow. This can be sped-up by loading a button there and generating the plots on button click.

Potential implementation pattern: https://github.com/bugbytes-io/django-htmx-studentlist/tree/master/%231-click-to-load

[s-sajid-ali]

Alternatively generate all usage plots overnight with a CronJob and load the html plots as needed, thereby removing plot generation time from the page loading time