Once T361174: Write to agent_id columns in the CheckUserInsert service when migration configuration allows it and T361172: Purge rows from cu_useragent are completed, extension.json should be updated to start writing to the cu_useragent table as well as the agent_id columns in the result tables. This is needed to be done before we can start to write to this table and columns on WMF wikis in T361196.
Acceptance criteria
- WMF wikis should have the schema migration config created in T361173 set to SCHEMA_COMPAT_OLD | SCHEMA_COMPAT_WRITE_NEW