As we are going to add a search tab in T185927, we want to make some changes to eventlogging SearchFunnel on iOS app to figure out the usage of it. Specifically, we'd like to:
- Add a `invoke_source` field to identify the source from which the search interface was invoked: the top of feed, the search tab, or from the article view
- Add a `langswitch` action when users tap on a different language on the search interface
- Add `is_anon`, `primary_language`, `session_id` fields to standardize it with other iOS eventlogging schemas
- Rename field `appInstallID` to `app_install_id`, `ts` to `event_dt`, to standardize it with other iOS eventlogging schemas
Schema: https://meta.wikimedia.org/w/index.php?title=Schema:MobileWikiAppSearch&oldid=18126493
Revision number: 18126493
We'd also like to add a `search_tab` field to [MobileWikiAppiOSUserHistory](https://meta.wikimedia.org/wiki/Schema:MobileWikiAppiOSUserHistory) to log whether the app opens to the new search tab.
**This task depends on T185927. If there is any design change in T185927, the spec may need to be changed accordingly.**