Welcome to Tailbone, part of the Rattail project. While the core Rattail package provides the data layer, the Tailbone package provides the (default, back-end) web application layer.
Some additional information is available on the website. Certainly not everything is documented yet, but here you can see what has received some attention thus far.
Quick Start for Custom Apps:
Need to fully implement
save_edit_row_form() for receiving batch.
(The original entry is located in /srv/buildbot/worker/tailbone/build/.tox/docs/lib/python3.9/site-packages/tailbone/views/purchasing/batch.py:docstring of tailbone.views.purchasing.batch.PurchasingBatchView.save_edit_row_form, line 22.)