As described in T320434#8741708, we should create a new table for storing tracking tools:
```lang=mysql
CREATE TABLE ce_tracking_tools (
cett_id BIGINT UNSIGNED AUTO_INCREMENT NOT NULL, -- Surrogate primary key
cett_event_id BIGINT UNSIGNED NOT NULL, -- Foreign key to campaign_events.event_id
cett_tool_id INT NOT NULL, -- Identifier of the tool, same as the existing campaign_events.event_tracking_tool_id
cett_tool_event_id BLOB NOT NULL, -- Identifier of the event within this tool, same as the existing campaign_events.event_tracking_tool_event_id
cett_sync_status INT NOT NULL, -- Status of the sync, the meaning of each value is defined in the application
cett_last_sync BINARY(14) NOT NULL -- Timestamp of the last synchronization
);
```
Also, `campaign_events.event_tracking_tool_id` and `campaign_events.event_tracking_tool_event_id` need to be dropped. Note that these fields can only be NULL for now.
==Acceptance criteria==
[] Create the new table and drop the old columns in the code
-- We don't need a backwards-compatible schema change for this: both production and the beta cluster use a database other than the wiki's local DB, meaning schema changes cannot be applied automatically anyway (related: T314908)
[] Adjust the code so that it reads from and writes to the new schema
-- This **needs** to be backwards-compatible, or things will break horribly
[] Create the new schema in beta (task TBC)
[] Create the new schema in production (task TBC)
[] Remove back-compat code