The `RecursiveCallbackDeveloper` and `ImmutableMethodDeveloper` classes
are not used anymore in tests, and neither is the `@Cancelled` variable.

`freeze` will ultimately end up freezing the `AttributeSet`, which in
turn freezes its `@attributes` hash. However, we actually insert a
special object to lazily instantiate the values of the hash on demand.
When it does need to actually instantiate all of them for iteration (the
only case is `ActiveRecord::Base#attributes`, which calls
`AttributeSet#to_h`), it will set an instance variable as a performance
optimization

Since it's just an optimization for subsequent calls, and that method
being called at all is a very uncommon case, we can just leave the ivar
alone if we're frozen, as opposed to coming up with some overly
complicated mechanism for freezing which allows us to continue to modify
ourselves.

Fixes #17960

The user is able to pass PG string literals in 4.1, and have it
converted to an array. This is also possible in 4.2, but it would remain
in string form until saving and reloading, which breaks our
`attr = save.reload.attr` contract. I think we should deprecate this in
5.0, and only allow array input from user sources. However, this
currently constitutes a breaking change to public API that did not go
through a deprecation cycle.

Also avoid using try since is_a? is faster for this case.

Make error message clearer that :on requires a symbol, not a string

fixing mailer previews for apps with globbing route

add brackets around attribute_name [ci skip]

since 'attr_name_will_change!' is not an actual method it should
be clearer that you have to insert the attribute name as in line 104

[ci skip]

Add note to Store about uniqueness validation (#17954) [skip ci]

Test coverage for ActiveJob generator

minor sentences fixes

The validation added in 5a3dc809 will
reject values for the `:on` option for after_commit and after_rollback
callbacks that are string values like `"create"`.

However, the error message says ":on conditions for after_commit and
after_rollback callbacks have to be one of create,destroy,update". That
looks like a string value *would* be valid.

This commit changes the error message to say ":on conditions for
after_commit and after_rollback callbacks have to be one of [:create,
:destroy, :update]", making it clearer that symbols are required.

Fix grammar of sentence in Reflection documentation [ci skip]

[ci skip] add `enable_extension` to PostgreSQL hstore example

Mounted Rack apps should have default named routes based on app name

[ci skip] update rails version to 3.2.21

Add Guides note to change cache namespace

This fixes a regression in 4.2.0 from 4.1.8.

https://github.com/rails/rails/pull/17823 fixed a similar regression regarding _explicitly_ named routes for a mounted Rack app, but there was another regression for the default value.

With a route like:

    Rails.application.routes.draw do
      mount Mountable::Web, at: 'some_route'
    end

The "Prefix" column of rake routes gives the following:

- 4.1.8:         mountable_web
- 4.2.0.beta1-4: [nothing]
- 4.2.0.rc1:     [nothing]
- 4.2.0.rc2:     some_route   <- regression

This fixes the default to go back to being based off the name of the class like the docs specify: https://github.com/rails/rails/blob/785d04e3109f69d0b9b9f4732179592f0ef04e52/actionpack/lib/action_dispatch/routing/mapper.rb#L558-L560

Explicitly named routes still work correctly per https://github.com/rails/rails/pull/17823:

    Rails.application.routes.draw do
      mount Mountable::Web, at: 'some_route', as: 'named'
    end

- 4.1.8:         named
- 4.2.0.beta1-4: [nothing]
- 4.2.0.rc1:     [nothing]
- 4.2.0.rc2:     named

If the tests are interupted and the teardown block doesn't run, the
developer needs to delete these manually in order to be able to run the
tests again.

The type registration was simply looking for the OID, and eagerly
fetching/constructing the sub type when it was registered. However,
numeric types have additional parameters which are extracted from the
actual SQL string of the type during lookup, and can have their behavior
change based on the result.

We simply need to use the block form of registration, and look up the
subtype lazily instead.

Fixes #17935

Fix grammar in Rakefile markup [ci skip]

Use latest web-console when using --dev or --edge

Fixes:

http://intertwingly.net/projects/AWDwR4/checkdepot-215/makedepot.log

remove unused `#generalized_table` and `#optional_parts`

This method was copied from journey at https://github.com/rails/rails/commit/56fee39c392788314c44a575b3fd66e16a50c8b5#diff-2cfaf53c860732fea8689d6f2002594bR78.
`grep -nr 'optional_parts' .`

This method wass copied from journey at https://github.com/rails/rails/commit/56fee39c392788314c44a575b3fd66e16a50c8b5#diff-d89de8881fc4b9f10cb3e4fc7b2463f3R53. However it looks the method was unused in journey at those point as well.

GlobalID objects are logged by their URI, not #inspect on the object, to prevent logging private data

Fix typo in "Hello World" template in German