Roadmap for 4.x

I've been working on 4.x behind the scenes and it will be a major rewrite of the module using more abstract code and more Drupal paradigms (I realize the two seem antonymous, but bear with me).

The current implementation of sitemap types consisting of URL and sitemap generators allows for a lot of flexibility and will be kept, but I intend to convert sitemap type plugins as well as sitemap variants to configuration entities.

Sitemaps will be instances of the sitemap variant entity type and they will be of a sitemap type (another configuration entity type). The sitemap type will define its sitemap generator and URL generators (plugins) as it does now.

In the process of implementing the above, I will try to further decouple the managing objects from the sitemap storage, so, if one was inclined, one could store the sitemaps as files instead of the database (crazy, I know :), or somewhere in the cloud).

The entity generating functionality as well as the custom link generating functionality will be decoupled as well. I have yet to decide if they will go into a submodule, or will be implemented as plugins

The functionality of the module will remain intact, its API will change drastically however. There will be an upgrade path for regular users who don't hook into the module's API.

Todo list:
See child issues.