Plumber adds a heap of useful bits and pieces to Umbraco, to allow multi-staged workflow approval for publish/unpublish actions.
In the backoffice, the new Workflow section has a documentation tab with detailed explanation of features and processes, or you can read the documentation here.
Noticed this repo doesn't have any code? That's because Plumber 2 is a licensed product, and the code is currently private. That may change in the future, but for the immediate future at least, it is how it is.
Plumber will always have a free version. It still requires a valid license, but comes at no cost. The free version does have some restrictions on features and functionality (5 group maximum, some advanced features disabled), but those aside, is still a full-featured solution and will be perfect for smaller, less complex implementations.
The paid license is a one-off, €900 one-time payment. All features, no restrictions, no ongoing cost.
There's a whole lot more boring stuff in the EULA.
Install-Package Plumber.Workflow
Drop a test license (an empty text file named test.lic) into /App_plugins/Plumber to impersonate the licensed version. The test license is restricted to naked localhost or localtest domains, or domains ending in .test or .local.