Make mutating params#dig return value mutate underlying params

Extract the confirm call in its own, overridable method in rails_ujs

Remove `ForeignKeys` module which was introduced at #32299

Not generate needless files in guides

Add AR::Base.base_class? predicate

Move SourceAnnotationExtractor under Rails module

Not generate needless files:

* _license.html.erb, _welcome.html.erb are partial files.
* layout.html.erb is the layout file.

To solve the problem #32299, just enough to introduce
`fk_ignore_pattern` option.

I don't think there is a need to expose these constants.

Fix typo in rails-ujs HTML content test

`</ps>` is not a valid closing tag for `<p>`.

Use consistent spacing in actionview helper docs

The spacing in these comments is fairly inconsistent. Array argument
contents are often separated with a space from the array literal
brackets but in several cases the Hash literal curly braces are tangent
to their contents which makes the documentation harder to read in some
cases.

Pass HTML responses as plain-text in rails-ujs

Change temporary file name extension while editing encrypted file.

Remove leftover blank sqlite3 file after in memory handler tests.

Move implementation of `before?` and `after?` to `DateAndTime::Calculations`

Fix two-level database configurations with URLs

Remove needless images in guides

This prevents duplication of code.

Prevent duplication of tests by moving them to `DateAndTimeBehavior`.

Related to #32185.

Deriving `secret_key_base` breaks `key_generator` defined in 5.1.

An entry in `ActiveRecord::Base.configurations` can either be a
connection spec ("two-level") or a hash of specs ("three-level").

We were detecting two-level configurations by looking for the `database`
key, but the database can also be specified as part of the `url` key,
which meant we incorrectly treated those configurations as three-level.

[ci skip] Use Oxford comma style in guide

If one created Rails 5.1 app and then updated to 5.2,
`secret_key_base` defined in `config/secrets.yml` is ignored for
`development` and `test` environment.
A change in `secret_key_base` in turn breaks
`Rails.application.key_generator`.

If one encrypt data in Rails 5.1, she cannot decrypt it in Rails 5.2
for `development` and `test` environment.

Fix: FileStoreTest#test_filename_max_size fails in Ruby 2.5.1

The text is a continuation of the sentence before the listing so
doesn't need to begin with a capital letter.

This reverts commit 77a7acaf.

[ci skip] Capitalize sentence of first char in AS guide

Add earlier releases v3.0, v3.1 in guides

Remove useless stylesheet file in guide

[ci skip] Modify twitter api link in api guide

* The twitter developer site's url was changed.