Merge pull request #12379 from francisgo/patch-7

Add new line after create action on CommentsController code example [ci skip]
Getting Started Guide: Update sentence in Chapter 5.8 [ci-skip]
Merge pull request #12233 from claudiob/delete-actionpack-unused-fixture

Remove HelperyTestHelper not used in any test
Merge pull request #12366 from francisgo/patch-4

Getting Started Guide: Update sentence in Chapter 5.8 [ci-skip]
Getting Started Guide: Fix code container in Chapter 5.2 [ci-skip]
Merge pull request #12385 from francisgo/patch-8

Getting Started Guide: Fix code container in Chapter 5.2 [ci-skip]
Fixed grammatical typo in configuring.md guide.
Fixed issue #12327
Merge pull request #12388 from rkofman/master

Fixed grammatical typo in configuring.md guide.
adding a test to demonstrate how to use STI subclasses on the far right
side of a hm:t association along with preloading.
Renamed generated_feature_methods to generated_association_methods.
Migrations Guide: Add semicolon to sentences before code block [ci skip]
Migrations Guide: Fix line length [ci skip]
Removed where_values_hash from AR::NullRelation

In order to build associated records for owners which has not been saved
need to get where values to use as default attributes.
But for new record owner uses `ActiveRecord::NullRelation` which
override `where_values_hash` to return empty hash stub.

`where_values_hash` is not used to invoke any sql query, but good to
build others chains (even will be never executed) like:

```ruby
  post          = Post.new
  admin_comment = post.admin_comments.build

  assert_equal 'Admin', admin_comment.author
```

Closes #11376, #11676, #11675
Merge pull request #12391 from francisgo/patch-10

Migrations Guide: Fix line length [ci skip]
Cleanup identitymap logger from LogSubscriber

Also renaming ivar @odd_or_even to @odd
Replace global Hash with TS::Cache.
Use TS::Cache instead of Mutex + Hash.

TS::Cache#compute_if_absent guarantees that only a single thread will get to execute the provided block for a given key.
Make GTG::TransTable thread safe.

From now on only the `[]=` method is allowed to modify the internal states hashes.
Merge branch 'master' of github.com:rails/docrails