More info on v5 changes

I work with Moodle and we've been migrating out legacy app to use Slim over the past 2 years.

I've just been looking through the 5.x branch to see how much the changes there are going to impact us but I'm finding that there isn't much information. The git commits aren't much help either because most of the commits contain seemingly unrelated changes under the banner 'Add v5'.

In particular:

• the changelog notes about using middleware for custom route arguments with the removal of Route::setArguments, but I can't actually see how you would do this without the Route. We use Route::setArguments() within a validation middleware to remove undeclared parameters.
• the \Slim\Interfaces\RouteInterface is just gone. No discussion, no alternative, no mention in the changelog. This is something that we use as type hints within our application and there is no apparent alternative or replacement
• no backwards compatibility available and no deprecation for many of these things (like Route::setArguments and fetching the Route from the Request attributes). We're an open source project and while we will be able to fix many of these things in our core platform, our community plugins are going to struggle a lot more to support a wide range of versions

Is there a plan or any discussion for the v5 changes? I'm aware of https://github.com/slimphp/Slim/wiki/Slim-5-Road-Map but none of these breaking changes are mentioned there, and there is no discussion about these. I haven't (yet) found a discussion in the discource channel either.

Start with the Slim 5 Road Map and the 5.x branch, then review the changes involving Route::setArguments, RouteInterface, and fetching the Route from Request attributes. Done would mean documenting the planned breaking changes, migration or replacement paths, and backwards-compatibility or deprecation decisions.