Remove Config\App Session items

[kenjis]

Description
Supersedes #7000

This PR is needed for #7308
Session should not depends on Config\App. See #4297 (comment)

• remove Config\App session items
• add property for Config\Session in Session

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[mostafakhudair]

Shall we add default config properties in system/Session/Session.php to avoid breaking app?, what if the developer removed some properties from app/Config/Session.php?

[kenjis]

what if the developer removed some properties from app/Config/Session.php?

It breaks.
If a dev removes Config\App::$baseURL now, the framework does not work.
It is not designed to work by removing necessary Config properties.

I don't see the significance of adding properties that just copies the properties of the Config class.

[kenjis]

Rebased to resolve conflicts.

Can anyone review?

[kenjis]

Rebased.

[iRedds]

This PR tries to get rid of the dependency on Config\App in Services::session() to prevent an infinite loop if the Config\App constructor is accessing a session.
But Services::session() depends on Services::request() which depends on Config\App.

That is, the call point of the infinite loop has shifted from Services::session() to Services::request().
Or am I wrong?

[kenjis]

@iRedds You are correct.
I started this to remove the infinite loop, but it is not possible with this PR.
See #7308 (comment)

But I think removing deprecated items in Config\App is worth doing.
It can remove code to fallback, and the code will be simpler.

We have already removed the deprecated Cookie items in Config\App:
https://github.com/codeigniter4/CodeIgniter4/blob/4.4/user_guide_src/source/installation/upgrade_440.rst#appconfigcookiephp

[iRedds]

Oh, I must have missed that comment. My bad.

[kenjis]

Rebased to resolve conflicts.

[kenjis]

I would like to merge this. Review, please.