As explained in T334761, we need to record when an organizer agrees to the "clickwrap agreement" for each event. We decided that this information will be stored into a new column in the ce_organizers table. Even if the application doesn't need the timestamp at the moment, and a boolean would suffice, we decided that we're going to store the timestamp anyway in case it's needed later.
===Acceptance criteria===
- A new column is added to ce_organizer to store the timestamp (or null) when the organizer agreed to the agreement.
- When the schema change has been merged in the code, two tasks should be created for applying this change and T339982 to Wikimedia wikis:
-- a task for beta
-- a #schema-change-in-production task for production
TODO: #schema-change-in-production task for this and T339982.