ActiveSupport::Duration.parse('P3Y') == 3.years # It should be true

Duration parsing made independent from any moment of time:
Fixed length in seconds is assigned to each duration part during parsing.

Changed duration of months and years in seconds to more accurate and logical:

 1. The value of 365.2425 days in Gregorian year is more accurate
    as it accounts for every 400th non-leap year.

 2. Month's length is bound to year's duration, which makes
    sensible comparisons like `12.months == 1.year` to be `true`
    and nonsensical ones like `30.days == 1.month` to be `false`.

Calculations on times and dates with durations shouldn't be affected as
duration's numeric value isn't used in calculations, only parts are used.

Methods on `Numeric` like `2.days` now use these predefined durations
to avoid duplicating of duration constants through the codebase and
eliminate creation of intermediate durations.

Deprecate reflection class name to accept a class

The idea of `class_name` as an option of reflection is that passing a
string would allow us to lazy autoload the class.

Using `belongs_to :client, class_name: Customer` is eagerloading models more than necessary
and creating possible circular dependencies.

ActionCable should not raise when a connection is already open

Update increment! documentation [ci skip]

Merge pull request #27604 from prathamesh-sonpatki/dont-generate-erb-views-for-api-scaffold-controller

Don't generate HTML/ERB templates for scaffold controller with --api flag

Fix random failure related to migration environment

Followup of #27596, test output of "run" method as well

Fix bug with symbolized keys in .where with nested join

- Fixes #27591.

- Reference: https://travis-ci.org/rails/rails/jobs/189764676

- Reproduction command:

    MTB_VERBOSE=2 bundle exec minitest_bisect --seed 33328 -Itest "test/cases/migration_test.rb" "test/cases/tasks/database_tasks_test.rb"

- You need to also add minitest_bisect gem to the Gemfile to reproduce
  this failure.

- #27596 Updated "run" and "migrate" method for returning correct
   value but only added test for "migrate" method. This commit adds a
   test for "run" as well.

Preserve `up` and `down` return type

Avoids a NoMethodError when table_name is a symbol instead of a string.

This will cause a failure with the changes from 8e2e5f9e:

https://github.com/rails/rails/commit/8e2e5f9e3d1f434e265dc104ea9b00ff75702fc3

With the `singularize` call that is being done in that method when there
is multiple nestings of associations (JOIN calling a JOIN) and the
`stringify_keys!` is only called once here:

https://github.com/rails/rails/blob/21e5fd4/activerecord/lib/active_record/relation/where_clause_factory.rb#L16

And not in the subsequent recursion in `.predicate_builder`

In Rails 4.2 calling `ActiveRecord::Migrator.migrate` would return an array of results. Without realizing that this return type was expected I accidentally introduced a change in https://github.com/rails/rails/commit/4d60e93174a3d6d90b1a06fc7515cb5cd749a6f3

This PR preserves the previous behavior and adds a test on the return type. This will need a backport to 5.0 branch.

ActionCable was throwing a "Existing connection must be closed before
opening" exception which was being picked up as a production issue in
our error monitoring software. Since this happens pretty often on any
device that allows the browser to sleep (mobile) this error was getting
triggered often.

This change removes the exception, but keeps logging the occurrence. We
now return `false` to let the caller now that `open` failed.

ensure `#compact` of HWIDA to return HWIDA

Allow to custom content type when setting mailer body

[documentation] ActiveRecord: Document order of Callbacks

Update `cookies` helper on all HTTP requests

`Hash#compact` of Ruby native returns new hash.
Therefore, in order to return HWIDA as in the past version, need to
define own `#compact` to HWIDA.

Related: #26868

Regression introduced by ae291421 / 8363b879.

Previously, cookies were only updated on `GET` requests. Now we will
update the helper for all requests, as part of `process`. Added
regression tests for all available HTTP method helpers in
`ActionController::TestCase`.

Actually, private methods cannot be called with `self.`, so it's not just redundant, it's a bad habit in Ruby

And let's see if it still fails...

this fixes sqlite3-1.3.12/lib/sqlite3/pragmas.rb:301: warning: method redefined; discarding old integrity_check

Optimizing information_schema query for `foreign_keys`

Need `table_name` to avoid all databases scan.
See https://dev.mysql.com/doc/refman/5.7/en/information-schema-optimization.html.

```
> EXPLAIN SELECT fk.referenced_table_name AS 'to_table', fk.referenced_column_name AS 'primary_key', fk.column_name AS 'column', fk.constraint_name AS 'name', rc.update_rule AS 'on_update', rc.delete_rule AS 'on_delete' FROM information_schema.key_column_usage fk JOIN information_schema.referential_constraints rc USING (constraint_schema, constraint_name) WHERE fk.referenced_column_name IS NOT NULL AND fk.table_schema = 'activerecord_unittest' AND fk.table_name = 'fk_test_has_pk' AND rc.table_name = 'fk_test_has_pk'\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: fk
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: TABLE_SCHEMA,TABLE_NAME
      key_len: NULL
          ref: NULL
         rows: NULL
     filtered: NULL
        Extra: Using where; Open_full_table; Scanned 0 databases
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: rc
   partitions: NULL
         type: ALL
possible_keys: NULL
          key: TABLE_NAME
      key_len: NULL
          ref: NULL
         rows: NULL
     filtered: NULL
        Extra: Using where; Open_full_table; Scanned 1 database; Using join buffer (Block Nested Loop)
2 rows in set, 1 warning (0.00 sec)
```

Fixes #27579.

We use aes-256-cbc cipher by default and it only accepts keys with 32
bytes at max.

Closes #27576.

[ci skip]

Clarify that mattr_* creates public methods

Add "check_parameters" option to "current_page?"

Fix typo in asset_pipeline.md [ci skip]

Require "models/post" before "models/comment"

Refer a similar pull request #26370