…ixtures

…alizer (#404)

* feat: add `split_expense_grouping` to the expense group settings serializer

* feat: implement split expense grouping functionality (#405)

* feat: implement split expense grouping functionality

* fix: skip only `expense_id` and `expense_number` while grouping

while defining the fields to group split expenses by, skip only `expense_id` and `expense_number`, NOT `spent_at` or `posted_at`

* feat: add script for split expense grouping (#406)

Set the default split expense grouping config to `SINGLE_LINE_ITEM` for all old orgs