Adapt to upcoming 1.9 release of Workflow

Problem/Motivation

I've been testing this module in the context of the latest dev-branch of Workflow module, which the maintainer is preparing for a 1.9 release. There are a number of known issues in 1.8 that they are seeking to fix, and so we want to prepare this module to make that jump as well.

Proposed resolution

Put this module through its paces against the latest dev-branch of Workflow, and maintain a patch (or perhaps new release branch, if the Workflow release is not imminent) to adapt our codebase to the modified API for Workflow 1.9.

Remaining tasks

I've already put together a basic patch that adapts to the latest codebase as of today (March 19, 2025). I'll post this here for now, and continue to track the updates in Workflow itself, posting updates here as needed.