The Inquiry and Donation models should be extended with a relationship to a Tracking entity.
The Tracking entity for donations should have the following fields:
The Tracking entity for memberships should have the following fields:
Maybe the wikiLogin field could also be migrated there (in a backwards-compatible way).
At the moment all these values are lumped in the data field of Membership and Donation.
See https://github.com/wmde/FundraisingStore/issues/36 for ideas on backwards- and forwards-compatibility.