"Active Users" count via a new "Logins" table

[sei-jbooz]

As a site admin, it would be good to know how many "Active Users" we have over a period of time. Providing this metric would require tracking when users login. This could be done via a new DB table that tracks a new row for "UserId logged in at this time" (potentially add "from this IP address" ?) -- open to other column suggestions

This new table should generally be "append only" -- adding a row every time a user logs in. The metrics from this table should surface in the "Site Usage Report"

[sei-bstein]

Probable columns:

• UserId
• DateTime
• agent string
• IP
• Access token end times?

Migration considerations - we have old counts of logins, so we'd either have to allow a lot of nullable columns (which I don't think is disastrous in this case) or just preserve the old count as a legacy thing ("... and 43 historical logins" or something). We'll discuss.

We should also use this occasion to ensure that we're capturing login events as intended. Right now, it appears that page refreshes trigger additional logins. Use of a unique identification of the token might help.