We have plugin support used in various places, some of these are documented to a greater or lesser extent (e.g SSO mapping providers), but we should have a generic doc they can all point to explaining:

1. How to write a plugin, e.g the function signatures of __init__ and parse_config, (see docs)
2. How to deploy these plugins in practice (i.e. make them a python package and install them in the venv?)