Add white-list for EventLogging auto-purging
[temporary location, replace before merging]
This file indicates which EventLogging database tables and fields
can be kept indefinitely and which ones, on the other hand, should
be deleted after 90 days.
- It's a TSV file.
- It has 2 columns: schema and field.
- It is a white-list, meaning that all schema-field pairs listed are to be kept indefinitely in the database. The rest of schema- field pairs not listed are to be auto-purged after 90 days.
- The schema column does not include the revision, just the schema name. This means the white-list applies to all revisions of a given schema. This is done on purpose, so that new revisions of a white-listed schema will continue to be considered. Otherwise, every time a schema got modified, we would need to add its fields to the white-list.
Note that new schemas or new fields in existing schemas will be
automatically auto-purged after 90 days by default. If a schema
owner wants their schema or fields to be kept indefinitely, they
can contact analytics and we'll update the white-list.