RentDesk 2.1: multi-branch, properly

Branch-scoped stock and reporting, a group view for owners, and the migration path from 2.0.

The short version

This is demo content. Replace it from Admin → Blog.

What we changed

Every post on this blog exists because somebody asked the question twice. Writing the answer down once is cheaper than answering it a third time, and it happens to be the only marketing that still works on developers.