Release 0.23

Refs simonw#520, simonw#766, simonw#774, simonw#775, simonw#776, simonw#777, simonw#778, simonw#780, simonw#781, simonw#782, simonw#783, simonw#784, simonw#785, simonw#788, simonw#790, simonw#791, simonw#793, simonw#794, simonw#795, simonw#796, simonw#797, simonw#798, simonw#799, simonw#800, simonw#801, simonw#806

Closes simonw#803

Note about Pydantic v1 support in changelog for 0.23a0

Refs simonw#520, simonw#775

Release 0.22

Refs simonw#737, simonw#742, simonw#744, simonw#745, simonw#748, simonw#752

Release 0.21

Refs simonw#717, simonw#728

Documentation for model.attachment_types, closes simonw#705

Release 0.19.1

Refs simonw#667

Release 0.19

Refs simonw#495, simonw#610, simonw#640, simonw#641, simonw#644, simonw#653

Release 0.19a2

Refs simonw#640

Release 0.19a1

Refs simonw#644

Release 0.19a0

Refs simonw#610, simonw#641