SdcController cleanup tasks

Thanks for the review!

• I think everybody would agree all of the things you listed should happen eventually.
• But they should not be required to happen now.

We need to be able to iterate quickly, without accumulating enormous MRs like we tend to do in Drupal core. In Drupal core this makes sense because it's already a consistent whole, but that's not yet true for Experience Builder.
In other words: for XB, we intentionally want to avoid the "every commit must be perfect" strategy that Drupal core uses.

I acknowledge this means outside participation is more difficult: what is in a "ready for detailed review" state vs "slapped together, don't bother to review" state? So I think that is the challenge we should solve rather than disallowing imperfect/incomplete MRs to be reviewed.

So I propose to introduce a way to convey this. Ideas:

1. an impossible to miss
   

   // ⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️
   // ⚠️ 🔨🧹  This file is an early iteration. Do not review in detail yet.   🧹🔨 ⚠️
   // ⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️
   

   at the top of the file

2. Issues like the one you created here make for excellent Novice tasks! 😊 So it's not like this is a wasted effort at all. Perhaps we should even intentionally call this out, by adding comments like // @todo Novice: inject service, // @todo Novice: introduce new permission, et cetera?
3. introduce src-rough (back end) and ui/src-rough (front end) directories
4. … something else?

Started adopting #4.1: https://git.drupalcode.org/project/experience_builder/-/merge_requests/2... 🤠

I'm going to update the issue summary to outline, to make this a great issue to sprint on at DrupalCon Barcelona :)

Nobody picked this up during DrupalCon. Narrowing scope. Removing dead routes should happen in 📌 Lift all methods out of `SdcController` into separate invokable services-as-controllers Needs work .