[wip][ENG-6165] monthly institutional-users metrics report

[aaxelb]

Purpose

compute counts on a monthly basis for each user with an institutional affiliation

Changes

• add osf.metrics.reports.InstitutionalUserReport
• add osf.metrics.reporters.InstitutionalUsersReporter

QA Notes

Please make verification statements inspired by your code and what your code touches.

• Verify
• Verify

What are the areas of risk?

Any concerns/considerations/questions that development raised?

Documentation

Side Effects

Ticket