You are interested in creating an OpenProject plugin? Great, here are some pointers to get you going.

Create an OpenProject plugin is a guide to get you started with a regular plugin.

Create an OmniAuth plugin shows you the steps to create a new OmniAuth plugin, which allows you to integration new authentication providers to OpenProject.

A working exemplary plugin that shows you the basic operations you can use is available here:
https://github.com/opf/openproject-proto_plugin