**Context**: Organizers can choose whether to enable contribution tracking, if their event qualifies (as defined in the parent task). This information needs to be stored into the database. We first considered implementing this as a new tracking tool, similar to the P&E Dashboard. However, we then decided to use an ad-hoc boolean flag instead, see details in T402468#11109118. This task tracks the associated schema change.
===Acceptance criteria===
- The `campaign_events` table gets a new boolean column that stores whether contribution tracking is enabled for that event.
- The column is created in beta and in production
===[[https://wikitech.wikimedia.org/wiki/Schema_changes#Workflow_of_a_schema_change | Checklist ]] ===
[x] Design the schema
[x] Tag this task with #schema-change
[] Make schema change patch for it
[] Get initial reviews and DBA feedback
[] Merge the schema patch
-- This will automatically create the new table in beta
[] Wait until the patch reaches production
[] T398664 Create a subtask requesting the schema change in production, following instructions in https://wikitech.wikimedia.org/wiki/Schema_changes#Workflow_of_a_schema_change (3rd bullet)