Anchor should not be appended when set to nil/false.

Fixes https://github.com/rails/rails/issues/17714.
Add changelog entry for .reflections API change

`.reflections` public API changed to return a String instead of a Symbol
as keys.

see commit 1f31488499111fdfce79d8dc1cc8fb008f7cdb25 and 6259e4e2dcca9a79f22f96658c33efe81936bc0d

[fixes #16928]
[fixes #17610]
Update reflections public API doc
Merge pull request #17718 from arthurnn/fixes_16928

Fixes 16928, improve reflections public API doc [ci skip]
Fix explanation for ActionDispatch::Callbacks.

ActionDispatch::Callbacks dose not run the prepare callbacks,
so change with comment on ActionDispatch::Callbacks.
Merge pull request #17719 from yui-knk/fix/rails_on_rack_guide

Fix explanation for ActionDispatch::Callbacks. [ci skip]
[ci skip] Dispatching is a verb :bow:

cc #17719
[ci skip] Fix class name of middleware.
[ci skip] Fix comment of ActionDispatch::Callbacks

cc ddce3dd
Merge pull request #17722 from yui-knk/fix/callbacks_comment

[ci skip] Fix comment of ActionDispatch::Callbacks
Specified beta branch for web-console gem
Merge pull request #17715 from tgxworld/fix_nil_anchor

Anchor should not be appended when set to nil/false.
Test using `ActionController::TestCase` with engines

Reference #17453

[Godfrey Chan, Washington Luiz]
Correct example in the engines testing guide [ci skip]

Reference #17453
Merge pull request #17723 from marocu/patch-1

Specified beta branch for web-console gem
Add a test for reflection keys as Strings, fixes #16928

See also PR: #17610
Merge pull request #17732 from rails/add-reflections-string-keys-test

Add a test for reflection keys as Strings, fixes #16928
Merge pull request #17721 from yui-knk/fix/rails_on_rack_guide

[ci skip] Fix class name of middleware.
Clarify what is being serialized and when it will be deserialized

[ci skip]
Grammar pass on Web Console release note [ci skip]