App Passwords: Fix success=false not being appended to fallback reject url

[TimothyBlynJacobs]

On the Authorize Application screen with a success_url of https://example.org, we display https://example.org?success=false as the rejection URL. However, the user is redirected to https://example.org, without success=false

Trac ticket: https://core.trac.wordpress.org/ticket/51581

@georgestephanis if you could review that'd be great!

[georgestephanis]

Added some thoughts about a logic path that this change messes with -- if both the success url and reject urls are omitted, this enters an odd fail state.

[georgestephanis]

With the latest changes it looks right to me. Do we have any integration testing or the like for core we could build against for this? It seems like it may be tricky to mock for unit testing.

[TimothyBlynJacobs]

There is a project to add end-to-end tests in Core, but I don't think we've formally started yet. There is a more recent update than this, ​https://make.wordpress.org/core/2019/06/27/introducing-the-wordpress-e2e-tests/, but I can't find it atm. ​https://github.com/WordPress/wordpress-develop/tree/master/tests/e2e/specs

[TimothyBlynJacobs]

In 49272:

App Passwords: Fix success=false not being appended to fallback reject url.

Props TimothyBlynJacobs, georgestephanis.
Fixes #51581.