Make the method BaseAuthManager.is_authorized_custom_view abstract

[vincbeck]

While testing auth managers I realized that is_authorized_custom_view is also called when custom pages are defined in plugins. Therefore, we need to make the method BaseAuthManager.is_authorized_custom_view abstract so that auth managers can also work in environments with custom pages defined in plugins.

This is technically a breaking change but:

• Auth managers have been introduced recently, I am very confident nobody used the interface yet
• Documentation related to auth managers have not been released yet (will be in 2.9), hence the likelihood of having user using the interface is even less
• This is a bug fix

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[o-nikolas]

I'm also a bit confused by the menu related changes.

Also is it possible to get unit test coverage of the plugin path? Since it was missed before

[vincbeck]

Hmmm, I can understand the MENU change looks unrelated. I can possibly split the PR in 2 if that helps. I can also a unit test to cover the plugin path

[vincbeck]

Actually, let me explain why I combined the two. The idea initially was to call is_authorized_custom_viewin this case: https://github.com/apache/airflow/blob/main/airflow/providers/amazon/aws/auth_manager/aws_auth_manager.py#L512. This case is when there is a custom menu item in the menu added by a plugin. This was my initial idea. But since recently in #37881 we added the action MENU, the idea was to use it as well. I can definitely do it in 2 PRs but that would mean implementing something with unit tests associated, and deleting this exact same code I just implemented in a follow-up PRs to take into consideration the action MENU.

Though, I am still happy to make this effort if you think that would make the review easier

[vincbeck]

I also added a unit test that loads the index page. The difference with the test being implemented in #37947, is this one is a unit test. No real API call is made against AWS. This test will fail as long as #37997 is not merged.

[vincbeck]

@o-nikolas @potiuk any concerns on why I also included the "MENU" change in this PR? Happy to change something if needed

[potiuk]

LGTM