**Request**: The VectorPrefDiffInstrumention created in T261842 currently sends all events to a stream called mediawiki.pref_diff. We'd like to create a new stream that is more specifically named (such as, mediawiki.skin_switch) to send these events to instead.
**Context**: The current stream name mediawiki.pref_diff seems like a generic, catch-all stream for all preference change events; however, its purpose is only to log user-initiated skin changes from the VectorPrefDiff Instrument. It's possible that a different instrument could use the same stream and log changes to other unrelated user preferences such as email. This is problematic as other preferences should be logged in separate streams so separate retention policies can be applied. For example, we'd like to retain skin switch data past 90 days but may not want to retain other user-sensitive properties past 90 days. As a result, we recommend changing the stream name for these events to something more specific to avoid confusion.
**Suggested Steps**:
1. Create new stream entry in mediawiki [[ https://gerrit.wikimedia.org/r/plugins/gitiles/operations/mediawiki-config/%2B/master/wmf-config/InitialiseSettings.php#21245 | config ]] file. Proposed new name: mediawiki.skin_switch or mediawiki.skin_diff
2. Change stream name in VectorPrefDiffInstrumentation
3. Update the Desktop Improvements Opt-Out Chart in [[ https://superset.wikimedia.org/r/665 | Superset Dashboard ]]
4. Add to the allowlist (Will be done in T287255)
**Developer Notes**:
- Added some POC patches to test adding new stream - testing locally, it appears to be working.
- Cloned the `pref_diff` schema, renamed it to `skin_diff`, updated the references in `skin_diff` and `VectorPrefDiffInstrumentation`.
- If this is the approach taken, once we verify that `skin_diff` is working, `pref_diff` can presumably be deleted in a follow up.