v5 Changes Working Doc

[jonchurch]

We have a doc now to collaborate on what is changing w/ v5. It's open to edits from anyone.

It exists as a way to try and pull together the changelog, and scratch for hashing out a migration guide and an announcement. But it's first goal is to serve as a reference for folks involved in the project, so we can all get a sense of what v5 is.

[jonchurch]

I updated the above doc to organize changes based on the system they relate to

In case the above gets destroyed somehow, I have this work in markdown format in a gist (it may not be up to date compared to the google doc depending on when you view it)

[jonchurch]

@dougwilson If you get a chance can you please review the "Changes by System" section of the google document? I see already that I have made a mistake in regard to the removal of app.param as pointed out in https://github.com/expressjs/express/pull/2649#issuecomment-628295150

I'll review these changes compared to the diff from the latest alpha against 4.17.1 tmr, to verify that the supposed changes are accurate

[dougwilson]

Yea, np. The app.param as a whole is still there, it's just the app.param(fn) signature that was removed -- that was the entire param middleware system; app.param(name, fn) is still valid and exists.