Create EES API attendance data

We need Attendance data for the dashboard that's compatible with the EES API. Currently the data are in the following files in the dashboard:
- Specifically for the dashboard
- attendance_data_dashboard.csv
- EES upload files that external users like to have access to:
- EES_daily_data.csv
- EES_weekly_data.csv
- EES_ytd_data.csv

The latter are actually just filtered versions of the former.

Thinking about the structure around absence filters, it looks something like the following:
- Attendance
- Present
- Late before registers closed
- Present am
- Present pm
- Approved educational activity
- Approved sporting activity
- Education off-site
- Work experience
- Dual registration
- Educational visit or trip
- Interview
- Overall absence
- Authorised absence
- Illness
- Medical or dental appointments
- Religious observance
- Study leave
- Traveller
- Holiday
- Exclusions
- Other
- Unauthorised absence
- Holiday
- Late after registers closed
- No reason yet
- Other

The third tier in the hierarchy are all effectively "reasons".

Note persistent absence is measured in terms of pupils rather than sessions so is a different "thing"

The Indicators would then be:
- Number of sessions
- Rate

Things that don't fit the above:
- Persistent absence (this is measured by pupil rather than session)
- Enrolments (number of pupils)
- Schools reporting
- Reported on GIAS
- Number of schools
- Schools reporting
- Reported on GIAS

I think all of the above can be organised along the following lines for the purposes of the API:
- Enrolments and persistent absence
- Pupil absence and reasons

The latter could be broken up in a number of ways if it's too bug:
- daily / weekly / year-to-date
- Headlines / reasons

Could maybe demo both options to see which works best