Migrate events table to include a deleted_on field and Soft Delete events from 2017 - 2018

[alexanderqchen]

Motivation

Right now, there's no way to actually delete events unless we send DELETE requests to /api/v1/event manually...however, we don't want to be able to actually delete the event from the database. Instead, we want to add a "deleted" field so that we won't render events that have been marked as deleted (while keeping the "deleted" events in the DB).

Look at this post to see how to write a migrations file

• update the event database to include a "deleted" column to enable soft deletes