Add breaking change page for completing Navigator behavior

[EArminjon]

Description of what this PR is changing or adding, and why:

A breaking change is planned along the PR bellow.

Issues fixed by this PR (if any):

flutter/flutter#157505

PRs or commits this PR depends on (if any):

flutter/flutter#157725

Presubmit checklist

• This PR is marked as draft with an explanation if not meant to land until a future stable release.
• This PR doesn’t contain automatically generated corrections (Grammarly or similar).
• This PR follows the Google Developer Documentation Style Guidelines — for example, it doesn’t use i.e. or e.g., and it avoids I and we (first person).
• This PR uses semantic line breaks of 80 characters or fewer.

[sfshaza2]

Overall, this looks great. Just a couple little nits.

@Piinks, we don't generally land breaking changes until the change goes into a release. Is this going into 3.29? I see that @chunhtai suggested in the flutter/flutter issue that the breaking change page needs to land before landing the change, but that's not how we generally do it. So, short version: can I land this now?

I believe this might be the first time EVER than a non-Googler has written a breaking change page!

[EArminjon]

Thank a lot for the review, changes requested applied :).

[sfshaza2]

/gcbrun

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit dd22da3):

https://flutter-docs-prod--pr11684-feat-navigator-complete-rou-cx62m8dr.web.app

[Piinks]

we don't generally land breaking changes until the change goes into a release.

This has never been the case. Guides for changes that have not been released yet are always listed under the "Not yet released to stable" section.

[sfshaza2]

OK, but they have generally landed into the main channel, which is what I meant.

[Piinks]

Ah ok! Yes. landing on the main channel in flutter/flutter, not a release. :)

[EArminjon]

Should i change the target branch of this PR ?

[chunhtai]

yup sorry if my previous comment in the pr confused you. Having this pr open and ready to land and announcement out in discord should be enough to land the framework change. Once that land you will need to get the version number by doing git describe --tags in the latest branch to fill out the timeline section and finally land this migration guide

[EArminjon]

For the discord part, I don't have the right to publish in the announcement channel. I've put a little message asking help inside the hackers-routing channel.

[EArminjon]

By "land the framework change" you mean the original PR where navigation is reworded right?

Original PR and this one needs to use a flutter version. There for the deprecation message and here for the timeline, I'm a bit confused to understand how I need to update that, in which order and how if one PR is merged.

[chunhtai]

Original PR and this one needs to use a flutter version. There for the deprecation message and here for the timeline, I'm a bit confused to understand how I need to update that, in which order and how if one PR is merged.

just use version before the merge

[chunhtai]

By "land the framework change" you mean the original PR where navigation is reworded right?

Right.

For the discord part, I don't have the right to publish in the announcement channel

I just sent out the announcement so no worry on this part.

[AlexV525]

Could we provide code examples before and after?

[EArminjon]

Done